#include<stdio.h>
#include<algorithm>
using namespace std;
struct ctq {
	double p,m;
	double h;


} a[10000];
bool cmp(ctq v,ctq b) {
	return v.h>b.h;
}

int main() {
	int n,t,i;
	double sum=0;
	scanf("%d%d",&n,&t);
	for(i=0; i<n; i++) {
		scanf("%lf%lf",&a[i].p,&a[i].m);
		a[i].h=1.0*a[i].p/a[i].m;
	}
	sort(a,a+n,cmp);
	for(i=0; i<n; i++) {
		if(t>a[i].p) {
			t-=a[i].p;
			sum+=a[i].m;
		} else {
			sum+=(a[i].p-t)*a[i].h;
			break;
		}
	}
	printf("%lf",sum);
	return 0;
}