#include<iostream>
#include<climits>
#include<fstream>
#include<algorithm>
using namespace std;
fstream fin("rucsac.in",ios::in),fout("rucscac.out",ios::out);
int s=0;
#define MAX 10001
struct obiect
{
    double g,v,e;
}x[MAX],aux;
int compara(obiect a,obiect b)
{
    return(a.e>b.e);
}
int main()
{
    int i,n,gmax,l;
    double castig=0;
    fin>>n>>gmax;
    for(i=1;i<=n;i++)
    {
        fin>>x[i].g>>x[i].v;
        x[i].e=x[i].v/x[i].g;
    }
    sort(x+1,x+n+1,compara);
    for(i=1;i<=n;i++)
    {
        if(s+x[i].g<=gmax)
        {
            castig+=x[i].v;
            s+=x[i].g;
        }
        else
        {
            l=gmax-s;
            castig+=l*x[i].e;
             s+=l;
            break;
        }
    }
    fout<<castig;
    fin.close();
    fout.close();
    return 0;
}