#include<iostream>
#include<cstdio>
using namespace std;
int main()
{
	int zhong[105];
	double jia[105],zongjia;
	int n,zongzhong;
	cin>>n>>zongzhong;
	for(int i=0;i<n;i++)
	{
		cin>>zhong[i]>>jia[i];
		jia[i]=jia[i]*1.0/zhong[i];
	}
	for(int i=0;i<n;i++)
	{
		for(int k=1;k<n;k++)
		{
			if(jia[k]>jia[k-1])
			{
				int temp=jia[k],tempp=zhong[k];
				jia[k]=jia[k-1];
				zhong[k]=zhong[k-1];
				jia[k-1]=temp;
				zhong[k-1]=tempp;
			}
		}
	}
	int sum=0,i=0;
	for(;sum<=zongzhong;)
	{
		for(int k=0;k<zhong[i];k++)
		{
			sum++;
			zongjia+=jia[i];
			if(sum==zongzhong)
			{
				printf("%.2f",zongjia);
				return 0;
			}
		}
		i++;
	}
}