func_code_string: #include <bits/stdc++.h>   using namespace std;   int n;   bool next_n(vector<int> &a) {     int i = n - 1;     for (; i >= 0 && a[i] == 5; --i) {       a[i] = 0;     }     if (i == -1) {       return false;     }     ++a[i];     return true;   }   int main() {     ios_base::sync_with_stdio(false);     cin.tie(0);     int m;     cin >> n >> m;     vector<vector<int>> graph(n);     int from, to;     for (int i = 0; i < m; ++i) {       cin >> from >> to;       --from;       --to;       graph[from].push_back(to);       graph[to].push_back(from);     }     vector<int> ns(n);     int answ = 0;     do {       set<pair<int, int>> ps;       for (int i = 0; i < n; ++i) {         for (int j : graph[i]) {           int a = ns[i];           int b = ns[j];           if (a > b) {             swap(a, b);           }           ps.emplace(a, b);         }       }       answ = max(answ, (int)ps.size());     } while (next_n(ns));     cout << answ;     return 0;   }   