func_code_string: #include <bits/stdc++.h>   using namespace std;   struct Result {     int u, v, w, z;   };   int N, M;   vector<vector<int>> edges, distances;   vector<vector<pair<int, int>>> D, R;   vector<int> enqueued;   int best = -1;   Result result;   int scan() {     auto c = getchar();     while (c <  0  || c >  9 ) c = getchar();     int n;     for (n = 0;  0  <= c && c <=  9 ; c = getchar()) n = n * 10 + c -  0 ;     return n;   }   void bfs(int start) {     queue<pair<int, int>> q;     q.push({start, 0});     enqueued[start] = start;     while (!q.empty()) {       auto &p = q.front();       q.pop();       D[start].push_back(p);       R[p.first].push_back({start, p.second});       distances[start][p.first] = p.second;       for (auto &v : edges[p.first]) {         if (enqueued[v] != start) {           q.push({v, p.second + 1});           enqueued[v] = start;         }       }     }   }   inline bool cmp(const pair<int, int> &a, const pair<int, int> &b) {     return a.second > b.second;   }   pair<int, int> find(const vector<pair<int, int>> &X, int a, int b, int c) {     for (auto &x : X) {       if (x.first != a && x.first != b && x.first != c) return x;     }     return {-1, -1};   }   void process() {     for (auto i = 0; i < N; i++) {       for (auto j = 0; j < N; j++) {         if (i == j || distances[i][j] == 0) continue;         do {           auto k = find(R[i], i, j, -1);           if (k.first == -1) break;           auto l = find(D[j], i, j, k.first);           if (l.first == -1) break;           auto value = k.second + l.second + distances[i][j];           if (value > best) {             best = value;             result = {k.first, i, j, l.first};           }         } while (false);         do {           auto l = find(D[j], i, j, -1);           if (l.first == -1) break;           auto k = find(R[i], i, j, l.first);           if (k.first == -1) break;           auto value = k.second + l.second + distances[i][j];           if (value > best) {             best = value;             result = {k.first, i, j, l.first};           }         } while (false);       }     }   }   int main() {     N = scan();     M = scan();     edges.resize(N);     distances.resize(N);     D.resize(N);     R.resize(N);     enqueued.resize(N);     fill(enqueued.begin(), enqueued.end(), -1);     for (auto i = 0; i < M; i++) {       auto x = scan() - 1;       auto y = scan() - 1;       edges[x].push_back(y);     }     for (auto i = 0; i < N; i++) {       vector<int> &v = edges[i];       sort(v.begin(), v.end());       v.resize(distance(v.begin(), unique(v.begin(), v.end())));       distances[i].resize(N);     }     for (auto i = 0; i < N; i++) bfs(i);     for (auto i = 0; i < N; i++) {       sort(D[i].begin(), D[i].end(), cmp);       sort(R[i].begin(), R[i].end(), cmp);     }     process();     printf( %d %d %d %d n , result.u + 1, result.v + 1, result.w + 1,            result.z + 1);   }   