#include<bits/stdc++.h>
using namespace std;
struct bw{
	double zl,jz;
	double xjb;
}a[105];
bool cmp(bw x,bw y)
{
	return x.xjb>y.xjb;
}
int main()
{
	int n;
	float t;
	float ans=0.0;
	scanf("%d %f",&n,&t);
	for(int i=1;i<=n;i++)
	{
		cin>>a[i].zl>>a[i].jz;
		a[i].xjb=a[i].jz/a[i].zl;
	}
	sort(a+1,a+n+1,cmp);
	for(int i=1;i<=n;i++)
	{
		if(a[i].zl>=t) ans+=a[i].jz,t-=a[i].zl;
		else{
			ans+=t*a[i].xjb;
			break;
		} 
	}
	printf("%.2f",ans);
	return 0;
}