#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, (h - sum + a[n-1]-1) / a[n-1]);
cout << ans << endl;
}