#include <fstream>
#include <algorithm>
#include <iostream>
using namespace std;
ifstream fin("energii.in");
ofstream fout("energii.out");
int G,W,EG[1005],CG[1005],V[1005][1005];
int energii()
{
    int i,j;
    for(i=1;i<=G;i++)
        for(j=W;j<=EG[i];j--)
                V[i][j]=max(V[i-1][j],V[i-1][j-EG[i]]+CG[i]);
    if(V[G][W]>=W)
        return V[G][W];
    return -1;
}
int main()
{
    fin>>G;
    fin>>W;
    for(int i=1;i<=G;i++)
        fin>>EG[i]>>CG[i];
    fout<<energii();
}