func_code_string: #include <bits/stdc++.h>   using namespace std;   template <class T>   int chkmax(T &a, T b) {     if (b > a) {       a = b;       return 1;     }     return 0;   }   template <class T>   int chkmin(T &a, T b) {     if (b < a) {       a = b;       return 1;     }     return 0;   }   template <class iterator>   void output(iterator begin, iterator end, ostream &out = cerr) {     while (begin != end) {       out << (*begin) <<    ;       begin++;     }     out << endl;   }   template <class T>   void output(T x, ostream &out = cerr) {     output(x.begin(), x.end(), out);   }   void fast_io() {     ios_base::sync_with_stdio(0);     cin.tie(0);     cout.tie(0);   }   const int MOD = 1e9 + 7;   const int _2 = (MOD + 1) / 2;   void add(int &a, int b) {     a += b;     if (a >= MOD) {       a -= MOD;     }   }   int mul(int a, int b) { return (1LL * a * b) % MOD; }   const int mx = 2e3 + 10;   int n, m, cs, used[mx];   vector<vector<int> > g;   vector<int> a;   void read() {     cin >> n >> m;     g.resize(n);     for (int i = 0; i < m; ++i) {       int u, v;       cin >> u >> v;       u--;       v--;       g[u].push_back(v);       g[v].push_back(u);     }   }   int dfs(int v) {     int res = 1;     used[v] = 1;     for (auto v1 : g[v]) {       if (used[v1] == 0) {         res += dfs(v1);       }     }     return res;   }   void find_cycles() {     used[0] = 1;     for (auto v : g[0]) {       if (used[v] == 0) {         int len = dfs(v);         a.push_back(len + 1);       }     }   }   int dp[mx][2 * mx], dpPref[mx][2 * mx], dpSuf[mx][2 * mx];   int dpPrefObl[mx][2 * mx], dpSufObl[mx][2 * mx];   void update_dp(int len, int idx, int stay) {     fill(dp[idx + 1], dp[idx + 1] + m + 1, 0);     for (int delta = 0; delta <= m; ++delta) {       if (dp[idx][delta]) {         add(dp[idx + 1][delta + len], dp[idx][delta]);         add(dp[idx + 1][abs(delta - len)], dp[idx][delta]);         if (stay) {           add(dp[idx + 1][delta], dp[idx][delta]);         }       }     }   }   void calc_dp(int stay) {     fill(dp[0], dp[0] + m + 1, 0);     dp[0][0] = 1;     for (int i = 0; i < cs; ++i) {       update_dp(a[i], i, stay);     }   }   void process() {     cs = a.size();     calc_dp(1);     for (int i = 0; i <= cs; ++i) {       copy(dp[i], dp[i] + m + 1, dpPref[i]);     }     calc_dp(0);     for (int i = 0; i <= cs; ++i) {       copy(dp[i], dp[i] + m + 1, dpPrefObl[i]);     }     reverse(a.begin(), a.end());     calc_dp(1);     for (int i = 0; i <= cs; ++i) {       copy(dp[i], dp[i] + m + 1, dpSuf[i]);     }     calc_dp(0);     for (int i = 0; i <= cs; ++i) {       copy(dp[i], dp[i] + m + 1, dpSufObl[i]);     }     reverse(a.begin(), a.end());   }   int ans;   int convert(int val, int pos) { return (pos == 0 ? val : mul(val, _2)); }   int merge(int pos, int sum) {     int res = 0;     for (int delta1 = -m; delta1 <= m; ++delta1) {       int delta2 = sum - delta1;       if (abs(delta2) <= m) {         add(res, mul(convert(dpPref[pos][abs(delta1)], delta1),                      convert(dpSuf[cs - 1 - pos][abs(delta2)], delta2)));       }     }     return res;   }   int merge_obl(int pos, int sum) {     int res = 0;     for (int delta1 = -m; delta1 <= m; ++delta1) {       int delta2 = sum - delta1;       if (abs(delta2) <= m) {         add(res, mul(convert(dpPrefObl[pos][abs(delta1)], delta1),                      convert(dpSufObl[cs - 1 - pos][abs(delta2)], delta2)));       }     }     return res;   }   void mergeAns() {     add(ans, dpPrefObl[cs][0]);     for (int i = 0; i < cs; ++i) {       add(ans, mul(merge_obl(i, a[i] - 1), 4));       for (int diff = 2 - a[i]; diff <= a[i] - 2; ++diff) {         add(ans, mul(merge(i, diff), 2));       }     }   }   signed main() {     fast_io();     read();     find_cycles();     process();     mergeAns();     cout << ans <<   n ;   }   