#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  long long H;
  int x;
  cin >> N >> H;
  long long a[100000], b[100000];
  for (int i = 1; i <= N; i++) {
    cin >> a[i] >> b[i];
    a[i] = max(a[i], a[i + 1]);
    x = a[i];
  }
  int sum = N;
  for (int j = 1; j <= N; j++) {
    if (x >= b[j]) {
      b[j] = 0;
      sum--;
    }
    H = H - b[j];
  }
  cout << (H + x - 1) / x + sum << endl;
  system("pause");
  return 0;
}
