func_code_string: #include <bits/stdc++.h>   using namespace std;   long long nChooseR(int n, int k);   long long gcd(long long a, long long b);   vector<string> split(string target, char c);   bool isPrime(long long g);   long long n, m, t, a[] = {0, 0, 1, 2, 3, 4, 5}, k, x, y, z;   long long ans;   map<pair<int, int>, int> mp;   vector<vector<int>> grid(7);   void solve(int i) {     for (auto u : grid[i]) {       if (mp[make_pair(a[i], a[u])] == 1) {         z++;         mp[make_pair(a[i], a[u])] = 0;         mp[make_pair(a[u], a[i])] = 0;         solve(u);       }     }   }   int main() {     ios_base::sync_with_stdio(false);     cin.tie(NULL);     cout.tie(NULL);     cin >> n >> m;     for (int i = 0; i < (int)(m); i++) {       cin >> x >> y;       x--;       y--;       grid[x].push_back(y);       grid[y].push_back(x);     }     do {       z = 0;       for (int i = 0; i < (int)(6); i++) {         for (int j = 0; j < (int)(6); j++) mp[make_pair(i, j)] = 1;       }       for (int i = 0; i < (int)(6); i++) solve(i);       ans = max(ans, z);     } while (next_permutation(a, a + 7));     cout << ans;     return 0;   }   long long nChooseR(int n, int k) {     if (k > n) return 0;     if (k * 2 > n) k = n - k;     if (k == 0) return 1;     long long result = n;     for (int i = 2; i <= k; ++i) {       result *= (n - i + 1);       result /= i;     }     return result;   }   long long gcd(long long a, long long b) { return b == 0 ? a : gcd(b, a % b); }   vector<string> split(string target, char c) {     string d =   ;     vector<string> arr;     for (auto n : target) {       if (n != c)         d += n;       else if (d !=   )         arr.push_back(d), d =   ;     }     if (d !=   ) arr.push_back(d), d =   ;     return arr;   }   bool isPrime(long long g) {     if ((g % 2 == 0 && g > 2) || g == 1) return 0;     for (long long i = 3; i * i <= g; i += 2)       if (g % i == 0) return 0;     return 1;   }   