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#include <cstdio>
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#include <iostream>
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#include <algorithm>
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#include <cmath>
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#include <cstring>
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using namespace std;
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const int maxn = 1e5 + 17;
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int T, n, b[maxn], a[maxn];
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string str;
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int main() {
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  cin >> T;
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  while(T--) {
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    cin >> n;
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    cin >> str;
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    for(int i = 1; i <= n; i++) b[i] = str[i - 1] - '0';
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    for(int i = 1; i <= n; i++) {
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      if(b[i]) {
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        if(b[i - 1]) {
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          a[i] = 1 - a[i - 1];
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        }
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        else {
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          a[i] = 1;
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        }
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      }
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      else {
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        if(b[i - 1]) {
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          a[i] = a[i - 1];
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        }
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        else {
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          a[i] = 1 - a[i - 1];
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        }
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      }
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    }
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    for(int i = 1; i <= n; i++) printf("%d", a[i]);
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    puts("");
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  }
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  return 0;
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}

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#include <cstdio>
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#include <iostream>
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#include <algorithm>
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#include <cstring>
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using namespace std;
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const int maxn = 1e6 + 17;
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int T, d, n = 1000000;
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int p[maxn], vis[maxn], cnt;
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int main() {
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  vis[0] = vis[1] = 1;
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  for(int i = 2; i <= n; i++) {
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    if(!vis[i]) p[++cnt] = i;
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    for(int j = 1; j <= cnt && 1ll * p[j] *i <= n; j++) {
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      vis[i * p[j]] = p[j];
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      if(!(i % p[j])) break;
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    }
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  }
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  // for(int i = 1; i <= 20; i++) cout << p[i] << endl;
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  cin >> T;
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  while(T--) {
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    cin >> d;
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    int p1, p2;
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    for(p1 = 1; p[p1] - 1 < d; p1++);
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    for(p2 = p1; p[p2] - p[p1] < d; p2++);
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    cout << 1ll * p[p1] * p[p2] << endl;
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  }
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  return 0;
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}

1
#include <cstdio>
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#include <iostream>
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#include <algorithm>
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#include <cstring>
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#include <vector>
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#define mp make_pair
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#define pb push_back
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using namespace std;
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typedef pair<int, int> pii;
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const int maxn = 2e6 + 17;
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int T, n, a[maxn], c[maxn];
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int ans[maxn][2], f;
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bool cmp(int x, int y) {
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  return x > y;
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}
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void dfs(int u, int p) {
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  while(c[a[p]] > 0 && p <= n * 2) p++;
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  if(p > n * 2) {
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    f = 1;
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    return;
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  }
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  int tmp = ans[u - 1][1] - a[p];
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  if(c[tmp] > 0) {
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    c[a[p]]--, c[tmp]--;
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    ans[u][0] = tmp, ans[u][1] = a[p];
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    dfs(u + 1, p + 1);
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    c[a[p]]++, c[tmp]++;
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  }
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}
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int main() {
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  scanf("%d", &T);
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  while(T--) {
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    int flg = 0;
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    scanf("%d", &n);
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    for(int i = 1; i <= 2 * n; i++) scanf("%d", &a[i]), c[a[i]]++;
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    sort(a + 1, a + 1 + 2 * n, cmp);
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    for(int i = 2; i <= n * 2; i++) {
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      f = 0;
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      ans[0][1] = a[1] + a[i];
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      dfs(1, 1);
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      if(f) {
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        puts("YES");
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        flg = 1;
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        printf("%d\n", ans[1][0] + ans[1][1]);
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        for(int j = 1; j <= n; j++) printf("%d %d\n", ans[j][0], ans[j][1]);
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        break;
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      }
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    }
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    if(!flg) puts("NO");
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    for(int i = 1; i <= 2 * n; i++) c[a[i]]--;
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  }
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  return 0;
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}