#include<bits/stdc++.h>
using namespace std;
int n,m;
double ans;
struct nm{
int cc,p;
double a;
}k[2000010];
bool cmp(nm x,nm y){
return x.a-y.a > 0.00000000001;
}
int main(){
cin >> n >> m;
for(int i=1;i<=n;i++){
cin >> k[i].p >> k[i].cc;
k[i].a=k[i].cc*1.0/(k[i].p*1.0);
}
sort(k+1,k+m+1,cmp);
for(int i=1;i<=m;i++){
if(m-k[i].p>0){
ans+=k[i].cc;
m-=k[i].p;
}else{
ans+=1.0*m*k[i].a;
break;
}
}
printf("%.2lf",ans);
}