#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

int main() {
    int N, W; cin >> N >> W;
    vector<pair<ll,ll>> items(N+1);
    for (int i = 1; i <= N; i++) {
        ll wi, vi; cin >> wi >> vi;
        items[i] = {wi, vi};
    }

    ll ans = 0;
    for (ll i = 0; i < (1<<N); i++) {
        ll capacity = W, value = 0;
        for (int j = 0; j < N; j++) {
            auto [wj, vj] = items[j + 1];
            if (((i >> j) & 1)) {
                if (capacity >= wj) {
                    capacity -= wj;
                    value += vj;
                } else {
                    value = -1;
                    break;
                }
            }
        }
        ans = max(ans, value);
    }

    cout << ans << endl;

    return 0;
}