#include<bits/stdc++.h> using namespace std; struct things{ int price; int num; int ave; }a[110]; int n,L; bool comp(things x,things y){ return x.ave>y.ave; } int main(){ cin>>n>>L; for(int i=0;i<n;i++){ cin>>a[i].price>>a[i].num; a[i].ave=a[i].price/a[i].num; } sort(a,a+n,comp); int sum_price=0; for(int i=0;i<n;i++){ if(L>=a[i].num){ sum_price+=a[i].price; L=L-a[i].num; }else{ sum_price+=a[i].ave*L; break; } } cout<<sum_price<<endl; return 0; }