#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;
    f>>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;
}