#include <bits/stdc++.h>   using namespace std;   int main() {     int i, j, k, n, t, blow, head, d, h, mx, mxd;     cin >> t;     while (t--) {       cin >> blow >> head;       mx = -1;       mxd = 0;       while (blow > 0) {         cin >> d >> h;         mx = max(mx, d - h);         mxd = max(mxd, d);         blow--;       }       if (mx <= 0 && mxd < head) {         cout << -1 << endl;         continue;       }       int val = (head - mxd) / (mx);       if ((head - mxd) % mx != 0) val++;       val++;       if (mxd >= head) val = 1;       cout << val << endl;     }     return 0;   }   