#include <fstream>

using namespace std;

ifstream fin("energii.in");
ofstream fout("energii.out");

int n, wtMax, wt[1003], v[1003], dp[1003][10003];

int main() {
    fin >> n >> wtMax;
    for(int i = 1; i <= n; i++) {
        fin >> wt[i] >> v[i];
    }
    fin.close();
    for(int i = 1; i <= n; i++) {
        for(int j = 1; j <= wtMax; j++) {
            if(j < wt[i]) {
                dp[i][j] = dp[i - 1][j];
            } else {
                dp[i][j] = max(dp[i - 1][j], v[i] + dp[i - 1][j - wt[i]]);
            }
        }
    }
    fout << (dp[n][wtMax] >= wtMax ? dp[n][wtMax] : -1);
    return 0;
}