//greedy + sortare 40 p

#include <fstream>
#include <algorithm>
using namespace std;

struct s_gen
{
int p,c;
};

int n,w,c_total;
s_gen gen[1000];

bool comp(s_gen a,s_gen b);

int main()
{
ifstream in("energii.in");
ofstream out("energii.out");

int i1;

//citire
in>>n>>w;

for(i1=0;i1<n;i1++)
	{
	in>>gen[i1].p;
	in>>gen[i1].c;
	}

sort(gen,gen+n,comp);

i1=0;
while(w>0)
	{
	w -= gen[i1].p;
	c_total += gen[i1].c;
	i1++;
	}

out<<c_total;

in.close();
out.close();
return 0;
}

bool comp(s_gen a,s_gen b)
{
if((double)a.p/(double)a.c != (double)b.p/(double)b.c)
	return ((double)a.p/(double)a.c > (double)b.p/(double)b.c);
else
	return (a.c < b.c);
}