#include <bits/stdc++.h>
using namespace std;
const int N = 105;
double single_value[N];
double item_room[N];
double room;
int times;
int main()
{
    cin >> times;
    cin >> room;

    int replace_times = times;
    int x = 1;
    while (replace_times--)
    {

        int total_room;
        int total_value;
        cin >> total_room >> total_value;
        item_room[x] = total_room;
        single_value[x] = total_value / total_room;
        x++;
    }
    sort(single_value + 1, single_value + 1 + times, greater<int>());
    double replace_room = room;
    int j = 1;
    double value_stack = 0;
    while (replace_room != 0)
    {
        if (replace_room >= item_room[j])
        {
            replace_room -= item_room[j];
            value_stack += single_value[j] * item_room[j];
        }
        else
        {
            value_stack += single_value[j] * replace_room;
            replace_room = 0;
        }
        j++;
    }
    printf("%.2lf", value_stack);
    return 0;
}