func_code_string: #include <bits/stdc++.h>   using namespace std;   inline int Get() {     int x = 0, f = 1;     char ch = getchar();     while (ch <  0  || ch >  9 ) {       if (ch ==  - ) f = -1;       ch = getchar();     }     while ( 0  <= ch && ch <=  9 ) {       x = (x << 1) + (x << 3) + ch -  0 ;       ch = getchar();     }     return x * f;   }   const long long mod = 1e9 + 7;   const long long Mod = 998244353;   int n, m;   long long f[2005][15];   struct road {     int to, next;   } s[2005 << 1];   int h[2005], cnt;   void add(int i, int j) {     s[++cnt] = (road){j, h[i]};     h[i] = cnt;   }   vector<int> e[2005];   long long fac[2005], ifac[2005];   long long ksm(long long t, long long x) {     long long ans = 1;     for (; x; x >>= 1, t = t * t % mod)       if (x & 1) ans = ans * t % mod;     return ans;   }   long long Hash[2005];   long long Hash2[2005];   const long long p = 666233, p2 = 134341;   unsigned long long p3 = 233333;   int size[2005];   bool cmp(int a, int b) {     if (size[a] != size[b]) return size[a] < size[b];     if (Hash[a] != Hash[b]) return Hash[a] < Hash[b];     return Hash2[a] < Hash2[b];   }   long long t[2005];   vector<int> sn[2005];   int dep[2005], mxdep[2005];   void dfs1(int v, int fr) {     size[v] = 1;     mxdep[v] = dep[v];     for (int i = 0; i < e[v].size(); i++) {       int to = e[v][i];       if (to == fr) continue;       sn[v].push_back(to);       dep[to] = dep[v] + 1;       dfs1(to, v);       mxdep[v] = max(mxdep[v], mxdep[to]);       size[v] += size[to];     }     sort(sn[v].begin(), sn[v].end(), cmp);     t[v] = 1;     for (int i = 0; i < sn[v].size(); i++) {       int j = i;       while (j + 1 < sn[v].size() && size[sn[v][i]] == size[sn[v][j + 1]] &&              Hash[sn[v][i]] == Hash[sn[v][j + 1]] &&              Hash2[sn[v][j]] == Hash2[sn[v][j + 1]])         j++;       t[v] = t[v] * ifac[j - i + 1] % mod;       i = j;     }     Hash2[v] = Hash[v] =  ( ;     long long now = 1, now2 = 1;     for (int i = 0; i < sn[v].size(); i++) {       Hash[v] = ((Hash[v] * now % mod) ^ Hash[sn[v][i]]) % mod;       Hash2[v] = ((Hash2[v] * now2 % Mod) ^ Hash2[sn[v][i]]) % Mod;       now = now * p % mod;       now2 = now2 * p2 % Mod;     }     Hash[v] = (Hash[v] * p +  ) ) % mod;     Hash2[v] = (Hash2[v] * p +  ) ) % Mod;   }   int st[2005], top;   int cal(int v, int u) {     if (!top) return 0;     static long long ans[1 << 13], g[1 << 13];     int num = sn[u].size();     for (int i = 0; i < 1 << num; i++) ans[i] = 0;     ans[0] = 1;     for (int i = 1; i <= top; i++) {       memcpy(g, ans, sizeof(g));       int now = st[i];       for (int j = 0; j < num; j++) {         if (!f[now][sn[u][j]]) continue;         int t = 1 << j;         for (int sta = 0; sta < 1 << num; sta++) {           if (!(sta & t))             g[sta | t] = (g[sta | t] + ans[sta] * f[now][sn[u][j]]) % mod;         }       }       memcpy(ans, g, sizeof(g));     }     return ans[(1 << num) - 1] * t[u] % mod;   }   long long ans;   int rt;   void solve(int v, int fr) {     for (int i = 1; i <= m; i++)       if (sn[i].size() == 0) f[v][i] = 1;     for (int i = h[v]; i; i = s[i].next) {       int to = s[i].to;       if (to == fr) continue;       solve(to, v);     }     top = 0;     for (int i = h[v]; i; i = s[i].next) {       if (s[i].to == fr) continue;       st[++top] = s[i].to;     }     for (int i = 1; i <= m; i++) {       if (sn[i].size()) {         f[v][i] = cal(v, i);       }     }     (ans += f[v][rt]) %= mod;   }   map<pair<int, int>, int> vis;   int work() {     for (int i = 1; i <= m; i++) sn[i].clear();     for (int i = 1; i <= m; i++) Hash[i] = Hash2[i] = 0;     dep[rt] = 1;     dfs1(rt, 0);     if (vis.find(make_pair(Hash[rt], Hash2[rt])) != vis.end()) return 0;     vis[make_pair(Hash[rt], Hash2[rt])] = 1;     memset(f, 0, sizeof(f));     ans = 0;     solve(1, 0);     return ans;   }   int main() {     n = Get();     int a, b;     for (int i = 1; i < n; i++) {       a = Get(), b = Get();       add(a, b), add(b, a);     }     m = Get();     fac[0] = 1;     for (int i = 1; i <= m; i++) fac[i] = fac[i - 1] * i % mod;     ifac[m] = ksm(fac[m], mod - 2);     for (int i = m - 1; i >= 0; i--) ifac[i] = ifac[i + 1] * (i + 1) % mod;     for (int i = 1; i < m; i++) {       a = Get(), b = Get();       e[a].push_back(b);       e[b].push_back(a);     }     long long tot = 0;     for (rt = m; rt >= 1; rt--) (tot += work()) %= mod;     cout << tot <<   n ;     return 0;   }   