#include<bits/stdc++.h>
using namespace std;
double sum,t;
long long n,i=1;
struct act
{
	long long m=10,v=7;
	double z;
}arr[10005];
bool mvp(act a,act b)
{
	return a.z>b.z;
}
int main()
{
	cin>>n>>t;
	for(int j=1;j<=n;j++)
	{
		scanf("%d%d",&arr[j].m,&arr[j].v);
		arr[j].z=(double)(arr[j].v)/(double)(arr[j].m);
	}
	sort(arr+1,arr+1+n,mvp);
	while(t!=0)
	{
		if(arr[i].m<=t)
		{
			t-=arr[i].m;
			sum+=arr[i].v;
		}
		else
		{
			sum+=t*arr[i].z;	
			break;
		}
		i++;
	}
	printf("%.2lf",sum);
	return 0;
}

第一个测试点WA了