#include using namespace std; #define FOR(i,a,b) for(int i=(a);i<(b);++i) #define REP(i,n) FOR(i,0,n) #define ALL(v) begin(v),end(v) template inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; } template inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; } using ll = long long; using pii = pair; constexpr ll INF = 1ll<<30; constexpr ll longINF = 1ll<<60; constexpr ll MOD = 1000000007; constexpr bool debug = false; //---------------------------------// /** * @brief https://tkmst201.github.io/Library/Mathematics/bit_operation.hpp */ namespace tk { constexpr int pop_count(std::uint32_t x) { x = (x & 0x55555555) + ((x >> 1) & 0x55555555); x = (x & 0x33333333) + ((x >> 2) & 0x33333333); x = (x + (x >> 4)) & 0x0f0f0f0f; x += x >> 8; x += x >> 16; return x & 0xff; } constexpr int count_trailing_zeros(std::uint32_t x) { return pop_count(~x & (x - 1)); } } // namespace tk int main() { int N; cin >> N; vector A(N); REP(i, N) scanf("%d", &A[i]); int ans = 0; auto dfs = [&](auto self, int s, int sum) { if (s == ~(~0 << N)) { chmax(ans, sum); return; } int res = 0, cur = ~s & ~(~0 << N); const int mn = tk::count_trailing_zeros(cur); s |= 1 << mn; cur ^= 1 << mn; while (cur > 0) { const int b = tk::count_trailing_zeros(cur); self(self, s | 1 << b, sum ^ (A[mn] + A[b])); cur ^= 1 << b; } }; dfs(dfs, 0, 0); cout << ans << endl; }