func_code_string: #include <bits/stdc++.h>   using namespace std;   int a[1010], ans[1010];   int main() {     int n, i, cur = 0, x, y, l1 = 1, l2 = 1;     cin >> n;     for (i = 1; i < n; i++) {       cin >> x >> y;       if (x > y) swap(x, y);       a[x]++;       if (y != n) {         cout <<  NO ;         return 0;       }     }     for (i = 1; i < n; i++) {       cur += a[i];       if (cur > i) {         cout <<  NO ;         return 0;       }     }     cout <<  YES  << endl;     ans[1] = n;     for (i = n - 1; i; i--) {       if (!a[i]) {         while (ans[l2]) l2++;         ans[l2] = i;         continue;       }       l1 += a[i];       ans[l1] = i;     }     for (i = 1; i < n; i++) cout << ans[i] <<     << ans[i + 1] << endl;     return 0;   }   