func_code_string: #include <bits/stdc++.h>   using namespace std;   template <class TH>   void _dbg(const char *sdbg, TH h) {     cerr << sdbg <<  =  << h << endl;   }   template <class TH, class... TA>   void _dbg(const char *sdbg, TH h, TA... a) {     while (*sdbg !=  , ) cerr << *sdbg++;     cerr <<  =  << h <<  , ;     _dbg(sdbg + 1, a...);   }   template <class L, class R>   ostream &operator<<(ostream &os, pair<L, R> p) {     return os <<  (  << p.first <<  ,   << p.second <<  ) ;   }   template <class Iterable,             class = typename enable_if<!is_same<string, Iterable>::value>::type>   auto operator<<(ostream &os, Iterable v) -> decltype(os << *begin(v)) {     os <<  [ ;     for (auto vv : v) os << vv <<  ,  ;     return os <<  ] ;   }   const int inf = 0x3f3f3f3f;   const long long infll = 0x3f3f3f3f3f3f3f3fll;   template <class T>   int sign(T x) {     return (x > 0) - (x < 0);   }   template <class T>   T abs(const T &x) {     return (x < T(0)) ? -x : x;   }   template <class T>   T gcd(T a, T b, T &x, T &y) {     if (b == 0) {       x = 1;       y = 0;       return a;     }     T x1, y1;     T d = gcd(b, a % b, x1, y1);     x = y1;     y = x1 - y1 * (a / b);     return d;   }   template <class T>   T mod_inverse(T a, T m) {     T x, y;     assert(gcd(a, m, x, y) == 1);     return (x % m + m) % m;   }   template <long long mod>   struct mod_num {     long long x;     explicit mod_num(long long x = 0) : x(x % mod) {}     mod_num operator+(mod_num b) { return mod_num(x + b.x); }     mod_num operator-(mod_num b) { return mod_num(x - b.x + mod); }     mod_num operator*(mod_num b) { return mod_num(x * b.x); }     mod_num operator/(mod_num b) { return mod_num(x * mod_inverse(b.x, mod)); }     mod_num operator^(long long e) {       mod_num ans(1);       mod_num b = *this;       for (; e; b = b * b, e /= 2)         if (e & 1) ans = ans * b;       return ans;     }     void operator+=(mod_num b) { x = (x + b.x) % mod; }   };   template <long long mod>   ostream &operator<<(ostream &os, mod_num<mod> x) {     return os << x.x;   }   vector<int> graph[512345];   int been[512345];   vector<int> st;   vector<vector<int>> rings;   vector<pair<int, int>> edges;   mod_num<1000000007> vertex_rings_factor[512345];   void dfs(int a, int p) {     been[a] = 1;     st.push_back(a);     for (int i = 0; i < ((int)(graph[a]).size()); i++) {       if (graph[a][i] != p) {         if (been[graph[a][i]] == 0)           dfs(graph[a][i], a);         else if (been[graph[a][i]] == 1) {           vector<int> tmp;           for (int j = ((int)(st).size()) - 1; st[j] != graph[a][i]; j--)             tmp.push_back(st[j]);           tmp.push_back(graph[a][i]);           rings.push_back(tmp);         }       }     }     st.pop_back();     been[a] = 2;   }   bool intersect(const vector<int> &v1, const vector<int> &v2) {     for (int i = 0; i < ((int)(v1).size()); i++)       if (find(v2.begin(), v2.end(), v1[i]) != v2.end()) return true;     return false;   }   int main() {     cin.sync_with_stdio(0);     cin.tie(0);     int n, m, a, b;     cin >> n >> m;     for (int i = 0; i < m; i++) {       cin >> a >> b;       edges.push_back({min(a, b), max(a, b)});       graph[a].push_back(b);       graph[b].push_back(a);     }     dfs(1, 1);     vector<mod_num<1000000007>> pot2div(max(11, n + 1));     pot2div[0] = mod_num<1000000007>(1);     pot2div[1] = pot2div[0] / mod_num<1000000007>(2);     for (int i = 2; i < ((int)(pot2div).size()); i++)       pot2div[i] = pot2div[i - 1] * pot2div[1];     mod_num<1000000007> sum_rings_factors(0);     for (int i = 0; i < ((int)(rings).size()); i++) {       sum_rings_factors += pot2div[((int)(rings[i]).size())];       for (int x : rings[i]) {         vertex_rings_factor[x] += pot2div[((int)(rings[i]).size())];       }     }     vector<mod_num<1000000007>> intersecting_rings_factors(((int)(rings).size()));     for (int i = 0; i < ((int)(rings).size()); i++)       for (int x : rings[i])         intersecting_rings_factors[i] +=             vertex_rings_factor[x] - pot2div[((int)(rings[i]).size())];     mod_num<1000000007> ex = (mod_num<1000000007>(2) ^ 0) *                                  mod_num<1000000007>(n) / mod_num<1000000007>(2) -                              mod_num<1000000007>(m) / mod_num<1000000007>(4);     for (int i = 0; i < ((int)(rings).size()); i++)       ex += pot2div[((int)(rings[i]).size())];     mod_num<1000000007> ex2(0);     mod_num<1000000007> ev2 =         mod_num<1000000007>(n) * mod_num<1000000007>(n - 1) /             (mod_num<1000000007>(2) ^ 2) +         mod_num<1000000007>(n) / (mod_num<1000000007>(2) ^ 1);     mod_num<1000000007> ee2(0);     for (int i = 0; i < m; i++) {       ee2 += pot2div[2];       ee2 += mod_num<1000000007>(((int)(graph[edges[i].first]).size()) +                                  ((int)(graph[edges[i].second]).size()) - 2) *              pot2div[3];       ee2 +=           mod_num<1000000007>(m - (((int)(graph[edges[i].first]).size()) +                                    ((int)(graph[edges[i].second]).size()) - 1)) *           pot2div[4];     }     mod_num<1000000007> er2(0);     for (int i = 0; i < ((int)(rings).size()); i++) {       er2 += pot2div[((int)(rings[i]).size())];       er2 +=           pot2div[((int)(rings[i]).size()) - 1] * intersecting_rings_factors[i];       er2 += pot2div[((int)(rings[i]).size())] *              (sum_rings_factors - intersecting_rings_factors[i] -               pot2div[((int)(rings[i]).size())]);     }     mod_num<1000000007> eve;     for (int i = 1; i <= n; i++) {       eve += mod_num<1000000007>(((int)(graph[i]).size())) * pot2div[2];       eve += mod_num<1000000007>(m - ((int)(graph[i]).size())) * pot2div[3];     }     mod_num<1000000007> eer;     for (int j = 0; j < ((int)(rings).size()); j++) {       int k = ((int)(rings[j]).size());       eer += mod_num<1000000007>(((int)(rings[j]).size())) *              pot2div[((int)(rings[j]).size())];       for (int x : rings[j]) {         eer += mod_num<1000000007>(((int)(graph[x]).size()) - 2) *                pot2div[((int)(rings[j]).size()) + 1];         k += ((int)(graph[x]).size()) - 2;       }       eer += mod_num<1000000007>(m - k) * pot2div[((int)(rings[j]).size()) + 2];     }     mod_num<1000000007> evr;     for (int i = 1; i <= n; i++) {       evr += vertex_rings_factor[i];       evr += (sum_rings_factors - vertex_rings_factor[i]) * pot2div[1];     }     ex2 = ev2 + ee2 + er2 - mod_num<1000000007>(2) * eve -           mod_num<1000000007>(2) * eer + mod_num<1000000007>(2) * evr;     cout << (mod_num<1000000007>(2) ^ (1000000007)) * (ex2 - ex * ex) *                 (mod_num<1000000007>(2) ^ (1000000005))          << endl;   }   