cpp

#include<iostream>
#include<algorithm>
#include<stdio.h>
using namespace std;
struct xjb {
	int w;
	int v;
	double x;
}a[110];
bool cmp(xjb a,xjb b)
{
	return a.x > b.x;
}
int main()
{
	int N, T;
	cin >> N >> T;
	for (int i = 0; i < N; i++)
	{
		cin >> a[i].w >> a[i].v;
		a[i].x = a[i].v*1.0 / a[i].w*1.0;
	}
	sort(a, a + N, cmp);
	int i = 0;
	double sum = 0;
	while (T>0)
	{
		while (a[i].w > 0)
		{
			if (T - 1 <0)
			{
				break;
			}
			T--;
			sum += a[i].x;
			a[i].w--;
		}
		i++;
	}
	printf("%.2lf", sum);
}