#include <fstream>
using namespace std;
ifstream fin("energii.in");
ofstream fout("energii.out");

const int WMAX = 5005;
const int NMAX = 1005;

int N, W, Max, Gmax, Cmin, ok;
int P[NMAX], G[NMAX], Sol[WMAX];

int main()
{
    fin >> N >> W;
    for(int i = 1; i <= N; i++)
        fin >> P[i] >> G[i], Gmax += G[i];

    for(int i = 1; i <= N; i++)
        for(int j = W - P[i]; j >= 0; j--)
            if(Sol[j + P[i]] < Sol[j] + G[i])
                Sol[j + P[i]] = Sol[j] + G[i];

    fout << (Sol[W] < W ? -1 : Sol[W]);
    return 0;
}