func_code_string: #include <bits/stdc++.h>   using namespace std;   const int N = 15;   const char inf =  z ;   bool g[N][N];   vector<string> gen_cand_strings(int n);   void rec_gen(vector<string>& ans, string& cur, char c, int n);   vector<string> get_good_strings(vector<string>& cand, int n);   vector<string> gen_cand2_strings(int n);   void rec_gen2(vector<string>& ans, string& cur, char c, int n);   bool is_ok(string s, vector<string>& good, int n);   bool is_ok_rec(string& s, vector<string>& good, vector<bool>& done, int c,                  int n);   int main() {     ios_base::sync_with_stdio(false);     cin.tie(NULL);     int n, m, k;     cin >> n >> m >> k;     for (int i = 0; i < m; ++i) {       int u, v;       cin >> u >> v;       --u;       --v;       g[u][v] = g[v][u] = 1;     }     vector<string> cand = gen_cand_strings(n);     vector<string> good = get_good_strings(cand, n);     sort(good.begin(), good.end());     vector<string> cand2 = gen_cand2_strings(n);     sort(cand2.begin(), cand2.end());     cand2.erase(unique(cand2.begin(), cand2.end()), cand2.end());     long long ans = 0;     for (auto& s : cand2) {       if (is_ok(s, good, n)) {         long long tmp = 1;         int cnt = *max_element(s.begin(), s.end()) + 1;         for (int i = 0; i < cnt; ++i) {           tmp *= (k - i);         }         ans += tmp;       } else {       }     }     cout << ans <<   n ;   }   vector<string> gen_cand_strings(int n) {     vector<string> ans;     string base(n, inf);     rec_gen(ans, base, 0, n);     return ans;   }   void rec_gen(vector<string>& ans, string& cur, char c, int n) {     for (int i = 0; i < n; ++i) {       if (cur[i] == inf) {         cur[i] = c;         for (int j = i + 1; j < n; ++j) {           if (cur[j] == inf) {             cur[j] = c;             rec_gen(ans, cur, c + 1, n);             cur[j] = inf;           }         }         cur[i] = inf;         return;       }     }     ans.push_back(cur);   }   vector<string> get_good_strings(vector<string>& cand, int n) {     vector<string> good;     for (auto& s : cand) {       vector<vector<int>> pos(n / 2);       for (int i = 0; i < n; ++i) {         pos[s[i]].push_back(i);       }       int tot = (1 << (n / 2));       vector<vector<int>> dp(tot, vector<int>(n / 2, 0));       for (int i = 0; i < n / 2; ++i) {         dp[(1 << i)][i] = g[pos[i][0]][pos[i][1]];       }       for (int mask = 0; mask < tot; ++mask) {         if (__builtin_popcount(mask) < 2) {           continue;         }         for (int i = 0; i < n / 2; ++i) {           if (!((mask >> i) & 1)) {             continue;           }           int u0 = pos[i][0], u1 = pos[i][1];           int submask = mask - (1 << i);           for (int j = 0; j < n / 2; ++j) {             if (dp[submask][j]) {               int v0 = pos[j][0], v1 = pos[j][1];               if ((g[u0][v0] and g[u1][v1]) or (g[u0][v1] and g[u1][v0])) {                 dp[mask][i] = true;                 break;               }             }           }         }       }       for (int i = 0; i < n / 2; ++i) {         if (dp[tot - 1][i]) {           good.push_back(s);           break;         }       }     }     return good;   }   vector<string> gen_cand2_strings(int n) {     vector<string> ans;     string base(n, inf);     rec_gen2(ans, base, 0, n);     return ans;   }   void rec_gen2(vector<string>& ans, string& cur, char c, int n) {     for (int i = 0; i < n; ++i) {       if (cur[i] == inf) {         for (int j = i + 1; j < n; ++j) {           if (cur[j] == inf) {             for (int nc = 0; nc <= c; ++nc) {               cur[i] = cur[j] = nc;               rec_gen2(ans, cur, max(int(c), nc + 1), n);               cur[i] = cur[j] = inf;             }           }         }         return;       }     }     ans.push_back(cur);   }   bool is_ok(string s, vector<string>& good, int n) {     vector<bool> done(n, 0);     return is_ok_rec(s, good, done, 0, n);   }   bool is_ok_rec(string& s, vector<string>& good, vector<bool>& done, int c,                  int n) {     if (c == n / 2) {       auto it = lower_bound(good.begin(), good.end(), s);       if (it != good.end() and *it == s) {         return true;       }     } else {       for (int i = 0; i < n; ++i) {         if (!done[i]) {           for (int j = i + 1; j < n; ++j) {             if (!done[j] and s[i] == s[j]) {               char tmp = s[i];               s[i] = s[j] = c;               done[i] = done[j] = true;               if (is_ok_rec(s, good, done, c + 1, n)) {                 return true;               }               s[i] = s[j] = tmp;               done[i] = done[j] = false;             }           }           break;         }       }     }     return false;   }   