#include <iostream>
#include <algorithm>
#include <iomanip>
using namespace std;
struct rucsac{int c,g;};
rucsac a[10000];
bool cmp(rucsac a,rucsac b)
{
    if(a.c*b.g>b.c*a.g)return true;
    else return false;
}
int main()
{int n,k,i,greut;
float cost;
cin>>n>>k;
for(i=1;i<=n;i++)
    cin>>a[i].g>>a[i].c;
    sort(a+1,a+n+1,cmp);
cost=greut=0;
i=1;
while(greut+a[i].g<=k)
    {
 greut=greut+a[i].g;
   cost=cost+a[i].c;
 i++;
}
k=k-greut;
cost=cost+k*a[i].c*1.0/a[i].g;
    cout<<fixed<<setprecision(2)<<cost;
    return 0;
}