#include<fstream>
#include<algorithm>
using namespace std;
ifstream f ("rucsac.in");
ofstream g("rucsac.out");
int n , gmax , s;
struct ob {
    int p;
    int gr;
    float x;
};
ob v[5001];
int test(ob t1 , ob t2)
{
    return (t1.x > t2.x) || ((t1.x == t2.x) && (t1.gr < t2.gr));
}
int main ()
{
    f >> n >> gmax;
    for (int i = 1; i <= n;++i)
    {
        f >> v[i].gr >> v[i].p;
        v[i].x = v[i].p / (v[i].gr + 0.0);
    }
    sort (v + 1 , v + n + 1 , test);
    for (int i = 1; i <= n; ++i)
    {
        if (gmax - v[i].gr >= 0)
        {
            s = s + v[i].p;
            gmax = gmax - v[i].gr;
        }
    }
    g << s << endl;
    g.close();
    return 0;
}