#include using namespace std; using ll = long long; constexpr char newl = '\n'; using Graph = vector< vector >; bool dfs(int cur, vector& memo, Graph& g, vector& order) { memo[cur] = 1; for (int nex : g[cur]) { if (memo[nex] == 2) continue; if (memo[nex] == 1) return false; if (!dfs(nex, memo, g, order)) return false; } memo[cur] = 2; order.push_back(cur); return true; } bool tsort(Graph& g, vector& order) { vector memo(g.size(), 0); for (int i = 0; i < g.size(); i++) { if (memo[i] != 0) continue; if (!dfs(i, memo, g, order)) return false; } // reverse(order.begin(), order.end()); return true; } // https://noshi91.hatenablog.com/entry/2019/03/31/174006 template struct ModInt { using u64 = std::uint_fast64_t; static constexpr u64 MOD = Modulus; u64 val; constexpr ModInt(const u64 x = 0) noexcept : val(x % MOD) {} constexpr ModInt operator+() const noexcept { return ModInt(*this); } constexpr ModInt operator-() const noexcept { ModInt res(*this); if (res.val != 0) res.val = MOD - res.val; return res; } constexpr bool operator==(const ModInt& rhs) const noexcept { return val == rhs.val; } constexpr bool operator!=(const ModInt& rhs) const noexcept { return val != rhs.val; } // prefix increment/decrement constexpr ModInt& operator++() noexcept { return *this += ModInt(1); } constexpr ModInt& operator--() noexcept { return *this -= ModInt(1); } // postfix increment/decrement constexpr ModInt operator++(int) noexcept { ModInt tmp(*this); ++*this; return tmp; } constexpr ModInt operator--(int) noexcept { ModInt tmp(*this); --*this; return tmp; } constexpr ModInt operator+(const ModInt& rhs) const noexcept { return ModInt(*this) += rhs; } constexpr ModInt operator-(const ModInt& rhs) const noexcept { return ModInt(*this) -= rhs; } constexpr ModInt operator*(const ModInt& rhs) const noexcept { return ModInt(*this) *= rhs; } constexpr ModInt operator/(const ModInt& rhs) const noexcept { return ModInt(*this) /= rhs; } constexpr ModInt& operator+=(const ModInt& rhs) noexcept { val += rhs.val; if (val >= MOD) val -= MOD; return *this; } constexpr ModInt& operator-=(const ModInt& rhs) noexcept { if (val < rhs.val) val += MOD; val -= rhs.val; return *this; } constexpr ModInt& operator*=(const ModInt& rhs) noexcept { val = val * rhs.val % MOD; return *this; } // prime Modulus only constexpr ModInt& operator/=(const ModInt& rhs) noexcept { return *this *= rhs.inv(); } // prime Modulus only constexpr ModInt inv() const noexcept { return pow(*this, MOD - 2); } }; template constexpr ModInt pow(ModInt x, std::uint_fast64_t n) { ModInt res(1); while (n) { if (n & 1) res *= x; x *= x; n >>= 1; } return res; } template istream& operator>>(istream& is, ModInt& x) { std::uint_fast64_t val; is >> val; x = ModInt(val); return is; } template ostream& operator<<(ostream& os, const ModInt& x) { return os << x.val; } using mint = ModInt<1000000007>; int main() { cin.tie(nullptr); ios::sync_with_stdio(false); int n; cin >> n; Graph g(n); for (int i = 1; i < n; i++) { int a, b; cin >> a >> b; --a; --b; g[a].push_back(b); } vector order; tsort(g, order); vector sum(n, 0), cnt(n, 0); mint ans = 0; for (int i : order) { for (int j : g[i]) { cnt[i] += cnt[j] + 1; sum[i] += sum[j] + cnt[j] + 1; } // cerr << i << ": " << sum[i] << " " << cnt[i] << newl; ans += sum[i]; } cout << ans << newl; return 0; }