#include <bits/stdc++.h>
using namespace std;
struct zhai{
    int zhong;
    double jia;
    int zhonghe;
}a[110];
bool cmp(zhai x,zhai y){
    return x.jia>y.jia;
}
int main(){
    int n,t;
    double q,sum=0;
    cin>>n>>t;
    for(int i=1;i<=n;i++){
        cin>>a[i].zhong>>q;
        a[i].jia=q/a[i].zhong;
        a[i].zhonghe=q;
    }
    sort(a+1,a+n+1,cmp);
    for(int i=1;i<=n;i++){
        if(t>=a[i].zhong){
            sum+=a[i].zhonghe;
            t-=a[i].zhong;
        }
        else{
            sum+=t*a[i].jia;
            printf("%.2lf",sum);
            return 0;
        }
    }
    return 0;
}