#include<iostream>
#include<fstream>
using namespace std;
int x[5005],p[5005],g,i,n,aux1;
float y[5005],aux,s;
int main()
{
ifstream cin("rucsac.in");
ofstream cout("rucsac.out");
cin>>n>>g;
for(i=1;i<=n;i++)
{
	cin>>x[i]>>p[i];
	y[i]=x[i]/p[i];
}
for(i=1;i<=n-1;i++)
	if(y[i]<y[i+1])
	{
		aux=y[i];
		y[i]=y[i+1];
		y[i+1]=aux;
		
		aux1=p[i];
		p[i]=p[i+1];
		p[i+1]=aux1;
		
		aux1=x[i];
		x[i]=x[i+1];
		x[i+1]=aux1;
	}
for(i=1;i<=n;i++)
	if(x[i]<=g)
	{
		g=g-x[i];
		s=s+p[i];
	}
	cout<<s;
return 0;
cin.close();
cout.close();
}