#include <fstream>
#include <algorithm>
using namespace std;
ifstream fin("rucsac.in");
ofstream fout("rucsac.out");
int n, m, i, j, g, sum, sumg;
struct rucsac
{
    int pret, gr;
}v[5005];
bool comp(rucsac a, rucsac b)
{
    if(a.pret>b.pret)
        return 1;
    if(a.pret==b.pret&&a.gr<b.gr)
        return 1;
    return 0;
}
int main()
{
   fin>>n>>g;
   for(i=1;i<=n;i++)
       fin>>v[i].gr>>v[i].pret;
    sort(v+1,v+n+1,comp);
    for(i=1;i<=n&&sumg+v[i].gr<=g;i++)
    {
        sum+=v[i].pret;
        sumg+=v[i].gr;
    }
    fout<<sum;
}