func_code_string: #include <bits/stdc++.h>   using namespace std;   static const int MXN = 20000 + 2;   const int mod = 998244353;   long long dis[MXN];   struct CostFlow {     static const long long INF = 102938475610293847LL;     struct Edge {       int v, r;       long long f, c;       Edge(int a, int b, int _c, int d) : v(a), r(b), f(_c), c(d) {}     };     int n, s, t, prv[MXN], prvL[MXN], inq[MXN];     long long fl, cost;     vector<Edge> E[MXN];     void init(int _n, int _s, int _t) {       n = _n;       s = _s;       t = _t;       for (int i = 0; i < n; i++) E[i].clear();       fl = cost = 0;     }     void add_edge(int u, int v, long long f, long long c) {       E[u].push_back(Edge(v, E[v].size(), f, c));       E[v].push_back(Edge(u, E[u].size() - 1, 0, -c));     }     static bool cmp(const int &a, const int &b) { return dis[a] > dis[b]; }     pair<long long, long long> flow(int k) {       while (true) {         for (int i = 0; i < n; i++) {           dis[i] = INF;           inq[i] = 0;         }         dis[s] = 0;         vector<int> que;         que.push_back(s);         while (!que.empty()) {           int u = que.back();           que.pop_back();           inq[u] = 0;           for (int i = 0; i < E[u].size(); i++) {             int v = E[u][i].v;             long long w = E[u][i].c;             if (E[u][i].f > 0 && dis[v] > dis[u] + w) {               prv[v] = u;               prvL[v] = i;               dis[v] = dis[u] + w;               if (!inq[v]) {                 inq[v] = 1;                 que.push_back(v);               }             }           }           if (u == s) {             sort(que.begin(), que.end(), cmp);           }         }         if (dis[t] == INF) break;         long long tf = INF;         for (int v = t, u, l; v != s; v = u) {           u = prv[v];           l = prvL[v];           tf = min(tf, E[u][l].f);         }         for (int v = t, u, l; v != s; v = u) {           u = prv[v];           l = prvL[v];           E[u][l].f -= tf;           E[v][E[u][l].r].f += tf;         }         if (dis[t] > 0) break;         cost += tf * dis[t];         fl += tf;         if (fl == k) break;       }       return {fl, cost};     }   } flow;   int val[1 << 20];   int Index;   void solve() {     int n, k;     scanf( %d %d , &n, &k);     int a[1 << 20];     for (int i = 0; i < (1 << n); i++) scanf( %d , &a[i]);     priority_queue<pair<int, pair<int, int>>, vector<pair<int, pair<int, int>>>,                    greater<pair<int, pair<int, int>>>>         pq;     for (int i = 0; i < (1 << n); i++) {       if (__builtin_popcount(i) & 1) {         for (int j = 0; j < n; j++) {           pq.push(make_pair(a[i] + a[i ^ (1 << j)], make_pair(i, i ^ (1 << j))));         }         while (pq.size() > 2 * n * k) pq.pop();       }     }     vector<pair<int, pair<int, int>>> v;     while (!pq.empty()) {       v.push_back(pq.top());       pq.pop();     }     for (int i = 0; i < n * k * 2 && i < v.size(); i++) {       int a = v[i].second.first, b = v[i].second.second;       if (!val[a]) {         val[a] = ++Index;       }       if (!val[b]) {         val[b] = ++Index;       }     }     flow.init(Index + 2, 0, Index + 1);     for (int i = 0; i < (1 << n); i++) {       if (val[i]) {         if (__builtin_popcount(i) & 1)           flow.add_edge(0, val[i], 1, -a[i]);         else           flow.add_edge(val[i], Index + 1, 1, -a[i]);       }     }     for (int i = 0; i < n * k * 2 && i < v.size(); i++) {       flow.add_edge(val[v[i].second.first], val[v[i].second.second], 1, 0);     }     printf( %lld n , -flow.flow(k).second);   }   int main() {     int t = 1;     for (int i = 1; i <= t; i++) {       solve();     }     return 0;   }   