#include <bits/stdc++.h>
using namespace std;
#define lalala ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
#define N 100005
#define pb push_back
#define ins insert
#define int long long int
#define p push
vector<int> v;
signed main(){
lalala;
int n,m;cin>>n>>m;
priority_queue<tuple<double,int,int>> pq;
for(int i=0;i<n;i++){
int a,b;cin>>a>>b;
pq.p({a/b,b,a});
}
int cev=0;
while(pq.size()&&m){
int val,wei;double x;tie(x,wei,val)=pq.top();pq.pop();
//wei*=-1;
if(m>=wei){
cev+=val;
m-=wei;
}
}
cout<<cev<<endl;
}
//abbsy
//dark modern
//monokai
//monokai dimmned
//tommorrow night blue
