#include <bits/stdc++.h> using namespace std; using ll = long long; struct Item { ll w, v; }; int main() { ios::sync_with_stdio(false); cin.tie(nullptr); int N; ll M; cin >> N >> M; vector<Item> a(N); for (int i = 0; i < N; i++) cin >> a[i].w >> a[i].v; int n1 = N / 2; int n2 = N - n1; vector<Item> A(a.begin(), a.begin() + n1); vector<Item> B(a.begin() + n1, a.end()); vector<pair<ll,ll>> SA; for (int mask = 0; mask < (1 << n1); mask++) { ll w = 0, v = 0; for (int i = 0; i < n1; i++) if (mask & (1 << i)) w += A[i].w, v += A[i].v; if (w <= M) SA.push_back({w, v}); } vector<pair<ll,ll>> SB; for (int mask = 0; mask < (1 << n2); mask++) { ll w = 0, v = 0; for (int i = 0; i < n2; i++) if (mask & (1 << i)) w += B[i].w, v += B[i].v; if (w <= M) SB.push_back({w, v}); } sort(SB.begin(), SB.end()); vector<pair<ll,ll>> goodB; ll best = -1; for (auto &p : SB) { if (p.second > best) { best = p.second; goodB.push_back(p); } } ll ans = 0; for (auto &x : SA) { ll wA = x.first, vA = x.second; ll remain = M - wA; int l = 0, r = (int)goodB.size() - 1, pos = -1; while (l <= r) { int m = (l + r) / 2; if (goodB[m].first <= remain) pos = m, l = m + 1; else r = m - 1; } if (pos != -1) ans = max(ans, vA + goodB[pos].second); else ans = max(ans, vA); } cout << ans<<endl; return 0; }