#include <fstream>
#include <algorithm>
using namespace std;
ifstream fin("rucsac.in");
ofstream fout("rucsac.out");
struct rucsac
{
    int g,p;
    float r;
};
rucsac v[1000];
bool comp(rucsac a,rucsac b)
{
    return(a.r>b.r);

}
int main()
{
    int n,i,S,G;
    fin>>n>>G;
    for(i=1;i<=n;i++)
    {
        fin>>v[i].g>>v[i].p;
        v[i].r=(float)v[i].p/v[i].g;
    }
    S=0;
    sort(v+1,v+n+1,comp);
    for(i=1;i<=n&&G>0;i++)
    if(v[i].g<=G)
    {
        G=G-v[i].g;
        S=S+v[i].p;
    }
    fout<<S;

    return 0;
}