#include <fstream>
#include<algorithm>
using namespace std;
ifstream in("rucsac.in");
ofstream out("rucsac.out");
struct obiect{
    int g,v;};
obiect x[5010];
int n,G,t;
bool cmp(obiect a, obiect b){
    return a.v>b.v;
}

int main()
{
    in>>n>>G;
    for (int i=1;i<=n;i++)
            in>>x[i].g>>x[i].v;
    sort(x+1,x+n+1,cmp);
    for (int i=1;i<=n;i++)
    {
        if (x[i].g<=G)
        {G-=x[i].g;
        t+=x[i].v;
        }
    }
    out<<t;
    return 0;
}