func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     int n, m, a, b, i, j, arr[1005] = {0};     cin >> n >> m;     for (i = 1; i <= m; i++) {       cin >> a >> b;       arr[a] = 1;       arr[b] = 1;     }     for (i = 1; i <= n; i++) {       if (arr[i] == 0) break;     }     cout << n - 1 << endl;     for (j = 1; j <= n; j++) {       if (i != j) {         cout << i <<     << j << endl;       }     }     return 0;   }   