func_code_string: #include <bits/stdc++.h>   using namespace std;   template <typename A, typename B>   ostream &operator<<(ostream &os, const pair<A, B> &p) {     return os <<  (  << p.first <<  ,   << p.second <<  ) ;   }   template <typename T_container, typename T = typename enable_if<                                       !is_same<T_container, string>::value,                                       typename T_container::value_type>::type>   ostream &operator<<(ostream &os, const T_container &v) {     string sep;     for (const T &x : v) os << sep << x, sep =    ;     return os;   }   const int mxN = 12, oo = 1e9;   bool g[12][12], used[13];   long long ans = 0;   int n = 12, k;   int a[12];   bool pused[6];   bool goodr(int i = 0, int d = 0) {     if (d == n - 2) return g[a[i]][a[i + 1]];     for (int to = 0; to < n; to += 2)       if (!pused[to]) {         if ((g[a[i]][a[to]] and g[a[i + 1]][a[to + 1]]) or             (g[a[i]][a[to + 1]] and g[a[i + 1]][a[to]])) {           pused[to] = true;           if (goodr(to, d + 2)) {             pused[to] = false;             return true;           }           pused[to] = false;         }       }     return false;   }   bool good() {     for (int i = 0; i < n; i += 2) {       pused[i] = true;       if (goodr(i)) {         pused[i] = false;         return true;       }       pused[i] = false;     }     return false;   }   set<array<char, 12>> s;   int eq = 0;   array<char, 12> equiv, mp, reale;   void normalize() {     fill(begin(mp), end(mp), -1);     int t = 0;     for (int i = 0; i < n; ++i) {       if (mp[equiv[i]] == -1) mp[equiv[i]] = t++;       reale[i] = mp[equiv[i]];     }   }   void rec2(int i = 0) {     if (i == n) {       normalize();       if (eq > k) return;       if (!s.count(reale)) {         int cur = 1;         for (int j = k - eq + 1; j <= k; ++j) {           cur *= j;         }         ans += cur;         s.insert(reale);       }       return;     }     equiv[a[i]] = eq;     equiv[a[i + 1]] = eq;     eq++;     rec2(i + 2);     eq--;     for (int j = 0; j < eq; ++j) {       equiv[a[i]] = j;       equiv[a[i + 1]] = j;       rec2(i + 2);     }   }   void rec(int i, int d = 0) {     while (used[i]) ++i;     if (i == n) {       if (good()) {         rec2();       }       return;     }     used[i] = true;     for (int j = i + 1; j < n; ++j)       if (!used[j]) {         used[j] = true;         a[d] = i;         a[d + 1] = j;         rec(i + 1, d + 2);         used[j] = false;       }     used[i] = false;   }   int main() {     int m;     cin >> n >> m >> k;     for (int i = 0; i < m; ++i) {       int u, v;       cin >> u >> v, --u, --v;       g[u][v] = true;       g[v][u] = true;     }     rec(0);     cout << ans <<   n ;   }   