#include <bits/stdc++.h>
using namespace std;
const int N = 1005, MOD = 1000000007, A = 233, B = 101, C = 40961;
int n, m, x, y, a[20][20], ha[20], siz[20], tg, fa2[20], dp[N][20], f[1 << 12],
    ans;
set<int> s;
int head[N], ecnt, head2[20], ecnt2;
struct edge {
  int to, nxt;
} e[N << 1], e2[40];
inline void add(int x, int y) {
  e[++ecnt] = {y, head[x]};
  head[x] = ecnt;
}
inline void add2(int x, int y) {
  e2[++ecnt2] = {y, head2[x]};
  head2[x] = ecnt2;
}
inline int mo(int x) { return x >= MOD ? x - MOD : x; }
inline int ksm(int a, int b) {
  int c = 1;
  while (b) {
    if (b & 1) c = 1ll * c * a % MOD;
    a = 1ll * a * a % MOD;
    b >>= 1;
  }
  return c;
}
inline bool cmp(int a, int b) { return ha[a] < ha[b]; }
void dfs1(int x) {
  int y, o = 1;
  siz[x] = 1;
  for (int i = head2[x]; i; i = e2[i].nxt)
    if ((y = e2[i].to) != fa2[x]) {
      fa2[y] = x;
      dfs1(y);
      a[x][++a[x][0]] = y;
      siz[x] += siz[y];
    }
  sort(a[x] + 1, a[x] + a[x][0] + 1, cmp);
  for (register int i = 1; i <= a[x][0]; i++)
    ha[x] = ha[x] << (siz[a[x][i]] << 1) | ha[a[x][i]];
  ha[x] = ha[x] << 1 | 1;
  for (register int i = 2; i <= a[x][0]; i++) {
    if (ha[a[x][i]] != ha[a[x][i - 1]]) o = 0;
    tg = 1ll * tg * ++o % MOD;
  }
}
void dfs2(int x, int fa) {
  int y, full;
  for (int i = head[x]; i; i = e[i].nxt)
    if ((y = e[i].to) != fa) dfs2(y, x);
  for (int i = 1; i <= m; i++) {
    memset(f, 0, sizeof(f));
    f[0] = 1;
    full = (1 << a[i][0]) - 1;
    for (int j = head[x]; j; j = e[j].nxt)
      if ((y = e[j].to) != fa)
        for (register int ii = full; ii >= 0; ii--)
          for (register int k = 1; k <= a[i][0]; k++)
            if (ii & 1 << k - 1)
              f[ii] = (f[ii] + 1ll * f[ii ^ 1 << k - 1] * dp[y][a[i][k]]) % MOD;
    dp[x][i] = f[full];
  }
}
int main() {
  scanf("%d", &n);
  for (register int i = 1; i < n; i++)
    scanf("%d%d", &x, &y), add(x, y), add(y, x);
  scanf("%d", &m);
  for (register int i = 1; i < m; i++)
    scanf("%d%d", &x, &y), add2(x, y), add2(y, x);
  for (int i = 1; i <= m; i++) {
    memset(a, 0, sizeof(a));
    memset(dp, 0, sizeof(dp));
    memset(ha, 0, sizeof(ha));
    tg = 1;
    fa2[i] = i;
    dfs1(i);
    if (s.count(ha[i])) continue;
    s.insert(ha[i]);
    tg = ksm(tg, MOD - 2);
    dfs2(1, 1);
    for (register int j = 1; j <= n; j++)
      ans = (ans + 1ll * dp[j][i] * tg) % MOD;
  }
  printf("%d", ans);
}
