func_code_string: #include <bits/stdc++.h>   using namespace std;   const int INF = 1e9 + 7;   const int MOD = 1e9 + 7;   const int MAXN = 1e6 + 3;   const double EPS = (1e-7);   int dcmp(double x, double y) { return fabs(x - y) <= EPS ? 0 : x < y ? -1 : 1; }   long long gcd(long long a, long long b) {     if (b == 0)       return a;     else       return gcd(b, a % b);   }   long long power(long long x, long long y) {     long long res = 1;     while (y > 0) {       if (y & 1) res = res * x;       y = y >> 1;       x = x * x;     }     return res;   }   int main() {     ios_base::sync_with_stdio(false);     cin.tie(NULL);     int n, m, v;     cin >> n >> m >> v;     int maxcon = ((n - 1) * (n - 2)) / 2 + 1;     if (m > maxcon or m < n - 1) {       cout << -1 << endl;     } else {       for (int i = 1; i <= n; i++) {         if (i != v) {           cout << i <<     << v <<    n ;           m--;         }       }       int pr = 1;       if (pr == v) {         pr++;       }       for (int i = 1; i <= n and m; i++) {         if (i != v and i != pr) {           for (int j = i + 1; j <= n and m; j++) {             if (j != v and j != pr) {               cout << i <<     << j << endl;               m--;             }           }         }       }     }   }   