#include<fstream>
using namespace std;
ifstream in("energii.in");
ofstream out("energii.out");
int main()
{
    int g,w,i,c,e,s;
    float a[1001],b[1001],u[1001],aux;
    in>>g;
    in>>w;
    for(i=1;i<=g;i++)
    {
        in>>b[i];
        in>>u[i];
    }
     for(i=1;i<=g;i++)
     {
         a[i]=b[i]/u[i];
     }
     while (c==0);
       {
            c=1;
            for(i=1;i<=g-1;i++)
            {
                if (a[i]<a[i+1])
                {
                    aux=b[i];
                    b[i]=b[i+1];
                    b[i+1]=aux;
                    aux=u[i];
                    u[i]=u[i+1];
                    u[i+1]=aux;
                    aux=a[i];
                    a[i]=a[i+1];
                    a[i+1]=aux;
                    c=0;
                }
            }
        }
         s=0;
         i=1;
         e=0;
     while((i<=g) && (e<w));
       {
           e=e+b[i];
         s=s+u[i];
         i++;
       }
     out<<s;
         return 0;
}