//asta e doar o aproximare greedy; se pare ca pe infoarena i-a 0 pct;
#include<fstream>
#include<algorithm>
#define DIM 5000

using namespace std; 
ifstream in("rucsac.in"); 
ofstream out("rucsac.out"); 

int N;
float G;
float castig_total; 
struct obiect
{
	int weight, profit;
    float raport;	
}O[DIM]; 

bool comp(const obiect &unu, const obiect &doi)
{
	return unu.raport > doi.raport;
}
int main()
{
	int i, local_profit, local_weight, gasit = 0;
	
	in >> N >> G; 
	for(i = 1; i <= N; i++) 
		{
			in >> O[i].weight >> O[i].profit; 
			O[i].raport = O[i].profit/O[i].weight;
	}
	
	sort(O+1, O+N+1, comp);
	i = 1;
	local_profit = 0; 
    local_weight = 0;
    while( local_weight < G && i <= N && !gasit )
    {
		if( O[i].weight <= G - local_weight )
			{
				local_weight += O[i].weight; 
		        local_profit += O[i].profit;
		}				
			
			else {
				castig_total = local_profit + (G-local_weight)*O[i].raport;
				gasit = 1;
			}
	i++;			
	}
	
	out << castig_total;
}