#include <iostream>
#include<algorithm>
using namespace std;
struct obiect
{
    int greu, val;
};
int n, gmax;
obiect a[1005];
bool comp(obiect A, obiect B)
{
    return A.val * B.greu > A.greu * B.val;
}
int main()
{
    cin >> n >> gmax;
    for(int i=1 ; i<=n ; ++i)
        cin >> a[i].greu >> a[i].val;

    sort (a + 1 , a + n + 1, comp);

    int g = 0 , i = 1;
    double rez = 0;
    while(i <= n)
    {
        if(g + a[i].greu <= gmax)
        {
            g += a[i].greu;
            rez += a[i].val;
            i ++;
        }
        else if(gmax - g > 0)
            {
                double factor = 1.0 * (gmax - g) / a[i].greu;
                g = gmax;
                rez += factor * a[i].val;
                i++;
            }
            else i = n + 1;
    }
    cout << rez;
    return 0;
}