func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     int t;     cin >> t;     while (t--) {       int n, x = 0, y = 0, p = 0, q = 0;       cin >> n;       bool ans = true;       for (int i = 1; i <= n; i++) {         cin >> p >> q;         if (p < x || q < y)           ans = false;         else if (q - y > p - x)           ans = false;         x = p;         y = q;       }       if (ans == true)         cout <<  YES  << endl;       else         cout <<  NO  << endl;     }   }   