func_code_string: #include <bits/stdc++.h>   using namespace std;   const int INF = 0x3f3f3f3f;   const double PI = acos(-1), eps = 1e-6;   const int dx[4] = {-1, 1, 0, 0}, dy[4] = {0, 0, -1, 1};   const int N = 1e6 + 5, M = 2e6 + 5, mod = 1e9 + 7;   int n;   int p[N], c[N];   int main() {     ios::sync_with_stdio(false);     cin.tie(0), cout.tie(0);     int T;     cin >> T;     while (T--) {       cin >> n;       bool success = true;       for (int i = 1, d = 0; i <= n; i++) {         cin >> p[i] >> c[i];         if (p[i] < c[i] || p[i] < p[i - 1] || c[i] < c[i - 1] || p[i] - c[i] < d)           success = false;         d = p[i] - c[i];       }       cout << (success ?  YES  :  NO ) << endl;     }     return 0;   }   