#include <bits/stdc++.h>
using namespace std;
ifstream fin("energii.in");
ofstream fout("energii.out");
int g,w;
struct generator
{ int c,e;};
generator a[1005];
void in()
{
    int i;
    fin>>g>>w;
    for(i=1;i<=g;i+=1)
        fin>>a[i].e>>a[i].c;
}
bool cmp(generator a,generator b)
{
    return (a.e*b.c>b.e*a.c);
}
void creeare()
{
    int e=0,c=0,i=1;
    while (e<w)
    {
        e+=a[i].e;
        c+=a[i].c;
        //fout<<e<<' ';
        i+=1;
    }
    fout<<c;
    
}
int main()
{
    in();
    sort(a+1,a+g+1,cmp);
    creeare();
    return 0;
}