#include <iostream>
#include <fstream>
using namespace std;
ifstream f("rucsac.in");
ofstream g("rucsac.out");
struct rucsac
{
    double r, x, y;
} v[1001];
void sortare(rucsac v[], int &n)
{
    for (int i = 1; i < n; i++)
        for (int j = i + 1; j <= n; j++)
        {
            if (v[i].r < v[j].r)
                swap(v[i], v[j]);
        }
}
int GMax, n, i, j;
double s = 0;
int main()
{
    f >> n >> GMax;
    for (i = 1; i <= n; i++)
    {
        f >> v[i].x >> v[i].y;
        v[i].r = (double)v[i].y / v[i].x;
    }
    sortare(v, n);
    for (i = 1; i <= n && GMax; i++)
    {
        if (v[i].x < GMax)
        {
            s += v[i].y;
            GMax -= v[i].x;
        }
        else
        {
            s += v[i].r * GMax;
            GMax = 0;
        }
    }
    g << s;
    return 0;
}