func_code_string: #include <bits/stdc++.h>   using namespace std;   const int MOD = 1e9 + 7;   int main() {     cin.tie(0), cout.tie(0);     ios::sync_with_stdio(false);     int t;     cin >> t;     while (t--) {       int n, l, r, now = 1;       cin >> n;       for (int i = 0; i < n; i++) {         cin >> l >> r;         if (now < l) {           now = l;         }         if (now <= r) {           cout << now <<    ;           now++;         } else {           cout << 0 <<    ;         }       }       cout << endl;     }   }   