func_code_string: #include <bits/stdc++.h>   using namespace std;   const uint64_t seed =       std::chrono::system_clock::now().time_since_epoch().count();   mt19937_64 rnd(seed);   const int MOD = 998244353;   struct Dinic {     struct Edge {       int from, to;       long long cap, flow;       Edge(int u, int v, long long c) : from(u), to(v), cap(c), flow(0) {}     };     int n, m, s, t;     vector<vector<int>> g;     vector<Edge> edges;     vector<int> dis;     vector<int> cur;     int curFlow;     vector<bool> cut;     Dinic(int n, int s, int t)         : n(n), s(s), t(t), g(n), dis(n), cur(n), cut(n, false) {       curFlow = 0;       cut[0] = true;     }     void addEdge(int from, int to, long long cap) {       edges.push_back(Edge(from, to, cap));       edges.push_back(Edge(to, from, 0));       m = edges.size();       g[from].push_back(m - 2);       g[to].push_back(m - 1);     }     bool bfs() {       fill(dis.begin(), dis.end(), n);       dis[s] = 0;       queue<int> qq;       qq.push(s);       int cnt = 0;       while (!qq.empty()) {         cnt++;         int len = qq.size();         while (len--) {           int p = qq.front();           qq.pop();           for (int a : g[p]) {             Edge &e = edges[a];             if (e.flow >= e.cap) continue;             if (dis[e.to] == n) {               dis[e.to] = cnt;               qq.push(e.to);             }           }         }       }       return dis[t] != n;     }     long long dfs(int x, long long a) {       if (x == t || a == 0) return a;       long long flow = 0, f;       for (; cur[x] < g[x].size(); cur[x]++) {         Edge &e = edges[g[x][cur[x]]];         if (e.cap > e.flow && dis[x] + 1 == dis[e.to] &&             (f = dfs(e.to, min(a, e.cap - e.flow))) > 0) {           flow += f;           e.flow += f;           edges[g[x][cur[x]] ^ 1].flow -= f;           a -= f;           if (a == 0) break;         }       }       return flow;     }     long long maxFlow() {       long long flow = 0;       while (bfs()) {         fill(cur.begin(), cur.end(), 0);         flow += dfs(s, INT_MAX);       }       return flow;     }     long long dfs2(int x, long long limit, vector<bool> &vis) {       vis[x] = true;       if (x == t) return limit;       for (int ne : g[x]) {         Edge &e = edges[ne];         if (e.cap > e.flow && !vis[e.to] && !cut[e.to]) {           int r = dfs2(e.to, min(limit, e.cap - e.flow), vis);           if (r > 0) {             e.flow += r;             edges[ne ^ 1].flow -= r;             return r;           }         }       }       return 0;     }     long long work(int node) {       int e1, e2;       for (int i = 0; i < g[t].size(); i++) {         if (edges[g[t][i]].to == node) {           e1 = g[t][i];           break;         }       }       for (int i = 0; i < g[node].size(); i++) {         if (edges[g[node][i]].to == t) {           e2 = g[node][i];           break;         }       }       g[t].erase(find(g[t].begin(), g[t].end(), e1));       g[s].push_back(e1);       edges[e1].from = s;       edges[e1].cap = 1e9;       edges[e2].to = s;       curFlow -= edges[e2].flow;       do {         vector<bool> vis(n, false);         vis[s] = 0;         long long f = dfs2(node, edges[e2].cap - edges[e2].flow, vis);         edges[e2].flow += f;         edges[e2 ^ 1].flow -= f;         curFlow += f;         if (f == 0) {           swap(cut, vis);           break;         }       } while (true);       return curFlow;     }   };   void solve(int caseNum) {     int n;     cin >> n;     vector<vector<int>> a(n, vector<int>(n));     for (int i = 0; i < n; i++) {       for (int j = 0; j < n; j++) {         cin >> a[i][j];       }     }     int dd[][2] = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};     Dinic dinic(n * n + 2, n * n, n * n + 1);     vector<pair<int, int>> nodes;     for (int i = 0; i < n; i++) {       for (int j = 0; j < n; j++) {         if (a[i][j] == -1) continue;         int n1 = i * n + j;         if (a[i][j] > 0) {           dinic.addEdge(n1, n * n + 1, 1e9);           nodes.push_back({a[i][j], n1});         }         for (int k = 0; k < 4; k++) {           int ii = i + dd[k][0];           int jj = j + dd[k][1];           if (ii < 0 || ii >= n || jj < 0 || jj >= n) continue;           int n2 = ii * n + jj;           dinic.addEdge(n1, n2, 1);         }       }     }     sort(nodes.begin(), nodes.end());     int p = 0;     long long ans = 0;     int last = 0;     long long lastF = 0;     while (p < nodes.size()) {       int q = p;       ans += (nodes[p].first - last) * lastF;       while (q < nodes.size() && nodes[q].first == nodes[p].first) {         int node = nodes[q].second;         dinic.work(node);         q++;       }       lastF = dinic.curFlow;       last = nodes[p].first;       p = q;     }     cout << ans <<   n ;   }   int main() {     std::ios::sync_with_stdio(false);     cin.tie(NULL);     cout.precision(10);     int T = 1;     for (int i = 1; i <= T; i++) {       solve(i);     }     cout.flush();     return 0;   }   