#include <fstream>
using namespace std;

ifstream f ("energii.in");
ofstream g ("energii.out");

int n,i,j,k,W,e[1003],c[1003],sol[5003];
char p[5003][1002];
void citire()
{
    f>>n>>W;
    for(i=0;i<n;i++) f>>e[i]>>c[i];
    f.close();
}
int main()
{
    bool gasit;
    citire();
    for(i=1;i<=W;i++)
    {
        gasit=0;
        for(j=0;j<n;j++)
        {
            if(e[j]<=i && sol[i-e[j]]!=-1)
            {
                if(sol[i-e[j]]+c[j]>sol[i])
                {
                    sol[i]=sol[i-e[j]]+c[j];
                    for(k=0;k<n;k++) p[i][k]=p[i-e[j]][k];
                    p[i][j]=1;
                    gasit=1;
                }
            }
            if(!gasit) sol[i]=-1;
        }
    }
    g<<sol[W];
}