#include <iostream>
#include <fstream>

using namespace std;

ifstream f("rucsac.in");
ofstream go("rucsac.out");

struct rucsac
{
    float p,g;
    float r;
};
int i,j,n,sum;
 float k,gmax;
    rucsac v[5001];
int main()
{
    f>>n>>gmax;
    for(i=1;i<=n;i++)
    {
        f>>v[i].g>>v[i].p;
        v[i].r=(float)(v[i].p/v[i].g);
    }
    for(i=1;i<=n-1;i++)
        for(j=i+1;j<=n;j++)
        if(v[i].r<v[j].r)
        swap(v[i],v[j]);
    i=1;
    while(gmax-v[i].g>0 and i<=n)
    {
        gmax=gmax-v[i].g;
        sum=sum+v[i].p;
        i++;
    }
    if(gmax>0)
    sum=sum+gmax*v[i].r;
    go<<sum;
    return 0;
}