#include<fstream>
#include<iostream>
#include<algorithm>
using namespace std;
ifstream fin("rucsac.in");
ofstream fout("rucsac.out");
struct ob
{ int gr;
  int pr;
};
int test(ob x,ob y)
{
    return x.pr>y.pr;
}
ob v[5001];
int g,n;
int main()
{
    fin>>n>>g;
    for(int i=1;i<=n;++i)
        fin>>v[i].gr>>v[i].pr;
    sort(v+1,v+n+1,test);
    int w=0,sol=0;
    int i=1;
    while(w+v[i].gr<=g)
    {
        w=w+v[i].gr;
        sol=sol+v[i].pr;
        ++i;
    }
    fout<<sol;
    fin.close();
    return 0;
}