#include <iostream>
#include <vector>
using namespace std ;
using ll = long long ;
ll n, c ;
vector<pair<ll, ll>> dt ;
int cando(ll v) {
   ll researchleft = (v - 1) * c ;
   ll flex = 0 ;
   ll lastleft = c ;
   for (auto i: dt) {
      ll cnt = min(v, 1 + (i.second - 1) / i.first) ;
      researchleft -= cnt-1 ;
      if (cnt == v)
         lastleft -= 1 + max(0LL, i.second - cnt * i.first) ;
      else
         flex++ ;
   }
   return lastleft >= 0 && researchleft + lastleft >= flex ;
}
int main() {
   cin >> n >> c ;
   dt.resize(n) ;
   for (ll i=0; i<n; i++)
      cin >> dt[i].second >> dt[i].first ;
   ll b = 2 ;
   ll hi = 1 ;
   for (; !cando(hi); b <<= 1)
      hi = b ;
   for (; b; b >>= 1)
      if (hi > b && cando(hi - b))
         hi -= b ;
   cout << (hi-1) << endl ;
}