func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     std::ios_base::sync_with_stdio(false);     cin.tie(NULL);     long long int t = 1, i = 0, j = 0, k = 0;     cin >> t;     while (t--) {       long long int n;       cin >> n;       long long int l[n], r[n];       for (i = 0; i < n; ++i) cin >> l[i] >> r[i];       long long int t = 0;       for (i = 0; i < n; ++i) {         ++t;       sg:         if (i < n) {           if (r[i] > t - 1 && l[i] <= t)             cout << t <<    ;           else if (r[i] > t - 1) {             cout << l[i] <<    ;             t = l[i];           } else {             cout <<  0  ;             ++i;             goto sg;           }         }       }       cout <<   n ;     }     return 0;   }   