#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, h;
  cin >> n >> h;
  vector<int> a(n), b(n);
  for (int i = 0; i < n; ++i) cin >> a[i] >> b[i];
  int ans = 1e9, sum = 0;
  for (int i = 0; i < n; ++i)
    sum += b[n - 1 - i],
        ans = min(ans, max(1, i + 1 + (h - sum + a[n - 1] - 1) / a[n - 1]));
  cout << ans << endl;
}
