#include using namespace std; #define rep(i,n) for(int i = 0; i < (n);i++) #define sz(x) int(x.size()) typedef long long ll; typedef long double ld; typedef pair P; typedef pair PL; constexpr int mod = 1e9+7; struct mint { ll x; // typedef long long ll; mint(ll x=0):x((x%mod+mod)%mod){} mint operator-() const { return mint(-x);} mint& operator+=(const mint a) { if ((x += a.x) >= mod) x -= mod; return *this; } mint& operator-=(const mint a) { if ((x += mod-a.x) >= mod) x -= mod; return *this; } mint& operator*=(const mint a) { (x *= a.x) %= mod; return *this;} mint operator+(const mint a) const { return mint(*this) += a;} mint operator-(const mint a) const { return mint(*this) -= a;} mint operator*(const mint a) const { return mint(*this) *= a;} mint pow(ll t) const { if (!t) return 1; mint a = pow(t>>1); a *= a; if (t&1) a *= *this; return a; } // for prime mod mint inv() const { return pow(mod-2);} mint& operator/=(const mint a) { return *this *= a.inv();} mint operator/(const mint a) const { return mint(*this) /= a;} }; istream& operator>>(istream& is, const mint& a) { return is >> a.x;} ostream& operator<<(ostream& os, const mint& a) { return os << a.x;} int main() { int n; cin >> n; vector deg(n, 0); vector> g(n); rep(i,n - 1) { int a, b; cin >> a >> b; a--; b--; g[a].emplace_back(b); deg[b]++; } int root = -1; for (int i = 0; i < n; i++) { if (!deg[i]) root = i; } vector dp1(n, 0), dp2(n, 0); mint res = 0; auto dfs = [&](auto& f, int u)->void{ dp1[u] += 1; for (auto v : g[u]) { dp1[v] += dp1[u]; f(f, v); dp2[u] += dp2[v]; } res += dp1[u] * dp2[u]; dp2[u] += 1; }; dfs(dfs, root); cout << res << endl; return 0; }