#include<stdio.h>
#include<stdlib.h>
typedef struct{
    int m;
    int mnoey;
    double price;
}pe;
int cmp(const void *a ,const void *b)
{
	return (*(pe*)a).price - (*(pe*)b).price?1:-1;
}
int main()
{
    pe a[110];
    int n ,t;
    scanf("%d%d",&n,&t);
    for(int i = 1 ; i <= n ; i++ )
    {
        scanf("%d%d",&a[i].m,&a[i].mnoey);
        a[i].price = a[i].mnoey*1.0 / a[i].m;
    }
    qsort(a,n,sizeof(pe),cmp);
    double sum_mnoey = 0 ;
    for(int i= 1 ; i <= n ; i++)
    {
        if(a[i].m <= t)
        {
            sum_mnoey += a[i].mnoey;
            t -= a[i].m;
        }
        else
        {
            sum_mnoey += t*1.0*a[i].price;
            t = 0;
        }
        if(!t)
        break;
    }
    printf("%.2lf",sum_mnoey);
    return 0;
}