#include <fstream>
#include <algorithm>
using namespace std;
ifstream f ("rucsac.in");
ofstream g ("rucsac.out");
int n , gmax , s ;
struct ob {
    int p ,gr;
    float x;
};
ob V[5001];
bool 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+= V[i].p;
            gmax -= V[i].gr;
        }
    }
    g << s << '\n';
    g.close();
    return 0;
}