#include <fstream>
#include <algorithm>

using namespace std;

ifstream f("rucsac.in");
ofstream g("rucsac.out");

struct rap
{
    short p,v;
};

bool cmp(rap p,rap q)
{
    if(p.p*q.v>p.v*q.p) return 1;
    return 0;
}

int main()
{
    short n,g,i,vo=0;
    int s=0;
    rap v[5001];
    f>>n>>g;
    for(i=1;i<=n;i++)
        f>>v[i].v>>v[i].p;
    sort(v+1,v+n+1,cmp);
    i=1;
    while(vo+v[i].v<=g&&i<=n)
    {
        s+=v[i].p;
        vo+=v[i].v;
        i++;
    }
    g<<s;
    return 0;
}