#include <bits/stdc++.h>
using namespace std;

struct coin{
	int v,m;
	double d;
}a[110];

bool cmp(coin x,coin y){
	return x.d>y.d;
}
double ans;
int main (){
	int n,t,s,tmp=0;
	scanf("%d%d",&n,&t);
	s=t;
	for (int i=1;i<=n;i++){
		scanf("%d%d",&a[i].m,&a[i].v);
		a[i].d=a[i].v/a[i].m;
	}
	sort(a+1,a+1+n,cmp);
	for(int i=1;i<=n;i++){
		if (a[i].m>s) {
			tmp=i;
			break;
		}
		s-=a[i].m;
		ans+=a[i].v;
		tmp=i;
	}
	if(s!=0)
		ans+=1.0*s/a[tmp].m*a[tmp].v;
	printf("%.2llf",ans);
		
	return 0;
}