#include <fstream>
#include<algorithm>
using namespace std;
ifstream f("energii.in");
ofstream out("energii.out");
int g,w,energie,cost;
struct vect{int e;int c;}v[1003];

bool cond(vect x, vect y)
{
    if(x.c>y.c) return 1;
    //if(x.c==y.c && x.e<y.e) return 1;
    return 0;
}

int main()
{
    int i;
    f>>g>>w;
    for(i=1;i<=g;i++)
        f>>v[i].e>>v[i].c;
    sort(v+1,v+g+1,cond);
    for(i=1;i<=g;i++)
    {
        cost+=v[i].c;
        energie+=v[i].e;
        if(energie>=w) break;
    }
    out<<cost<<'\n';
    f.close();
    out.close();
    return 0;
}