#include<stdio.h>
struct don
{
	int dan,many;
	double ,number;
	
}a[100];
int main()
{
	double sum1=0;
	int n,t,j,k,m=0,sum=0;
	struct don p;
	scanf("%d%d",&n,&t);
	for(int i=0;i<n;i++)
	{
		scanf("%d%d",&j,&k);
		a[i].number=j;
		a[i].many=k;
		a[i].dan=k/j;
		//printf("%lf\n",a[i].dan);
	}
	for(int i=0;i<n;i++)
	{
		for(int l=0;l<n-i-1;i++)
		
		{
	    if(a[l].dan<a[l+1].dan)
			{
			p=a[l+1];
			a[l+1]=a[l];
			a[l]=p;
				
				
			}
		}
	}
	
	while(t>0)
	{
		if(t>=a[m].number)
		{
			t-=a[m].number;
			sum1+=a[m].many;
			
		}
		
		else
		{
			sum1+=t*a[m].dan;
			break;
			
		}
		
		m++;
		
	}
	
	
	
	
	printf("%.2llf",sum1);
	return 0;
}