func_code_string: #include <bits/stdc++.h>   using namespace std;   const long long maxn = 1e6 + 5;   const int INF = 0x7fffffff;   bool p(long long a) {     for (long long i = 2; i <= sqrt(a); i++) {       if (a % i == 0) return 0;     }     return 1;   }   int main() {     int n;     cin >> n;     int c = n;     while (!p(c)) {       c++;     }     cout << c <<   n ;     for (int i = 1; i < n; i++) cout << i <<     << i + 1 <<   n ;     cout << 1 <<     << n <<   n ;     for (int i = 1; i <= c - n; i++) cout << i <<     << n - i <<   n ;   }   