#include<bits/stdc++.h>
using namespace std;
struct coin{
double m,v;
double p;
};
bool cmp(coin x,coin y){
return x.p>y.p;
}
coin a[101];
double sum=0;
int main(){
int n,t;
cin>>n>>t;
for(int i=1;i<=n;i++){
cin>>a[i].m>>a[i].v;
a[i].p=(a[i].v*1.0)/(a[i].m*1.0);
}
sort(a+1,a+n+1,cmp);
for(int i=1;i<=n;i++){
if(t>=a[i].m){
t-=a[i].m;
sum+=a[i].v;
}
else{
sum+=t*a[i].p;
break;
}
}
printf("%.2lf",sum);
return 0;
}