using System; using System.IO; using System.Collections.Generic; using System.Linq; using System.Numerics; namespace AtCoder.Contest.C { static class Program { public static void Solve(Scanner cin) { int n = cin.ReadInt(); var (a, b) = cin.ReadValueArray(n - 1); for (int i = 0; i < n - 1; i++) { a[i]--; b[i]--; } var children = new List>(); var parent = new int[n]; var depth = new long[n]; for (int i = 0; i < n; i++) { children.Add(new List()); parent[i] = -1; } for (int i = 0; i < n - 1; i++) { children[a[i]].Add(b[i]); parent[b[i]] = a[i]; } var root = 0; for (int i = 0; i < n; i++) { if (parent[i] == -1) root = i; } var q = new Queue(); q.Enqueue(root); depth[root] = 0; while (q.Count > 0) { var now = q.Dequeue(); var nextdepth = depth[now] + 1; foreach (var e in children[now]) { depth[e] = nextdepth; q.Enqueue(e); } } ModInt ans = 0; for (int i = 0; i < n; i++) { ans += depth[i] * (depth[i] + 1) / 2; } Console.WriteLine(ans); } public static void Main(string[] args) { var sw = new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false }; Console.SetOut(sw); var cin = new Scanner(); Solve(cin); Console.Out.Flush(); } public static void YESNO(bool condition) { if (condition) Console.WriteLine("YES"); else Console.WriteLine("NO"); } public static void YesNo(bool condition) { if (condition) Console.WriteLine("Yes"); else Console.WriteLine("No"); } public static void yesno(bool condition) { if (condition) Console.WriteLine("yes"); else Console.WriteLine("no"); } } public struct ModInt : IComparable, IEquatable { public static long MOD = 1000000007; private readonly long num; public ModInt(long n) { num = n; } public override string ToString() => num.ToString(); public static ModInt operator +(ModInt l, ModInt r) { long x = l.num + r.num; if (x >= MOD) x -= MOD; return new ModInt(x); } public static ModInt operator -(ModInt l, ModInt r) { long x = l.num - r.num; if (x < 0) x += MOD; return new ModInt(x); } public static ModInt operator *(ModInt l, ModInt r) => new ModInt((l.num * r.num) % MOD); public static ModInt operator /(ModInt l, ModInt r) => l * r.Inverse(); public static ModInt operator ++(ModInt x) { var tmp = x + new ModInt(1); return tmp; } public static ModInt operator --(ModInt x) { var tmp = x - new ModInt(1); return tmp; } public static bool operator >(ModInt l, ModInt r) => l.CompareTo(r) > 0; public static bool operator <(ModInt l, ModInt r) => l.CompareTo(r) < 0; public static bool operator >=(ModInt l, ModInt r) => l.CompareTo(r) >= 0; public static bool operator <=(ModInt l, ModInt r) => l.CompareTo(r) <= 0; public static bool operator ==(ModInt l, ModInt r) => l.Equals(r); public static bool operator !=(ModInt l, ModInt r) => !l.Equals(r); public static implicit operator long(ModInt x) => x.num; public static implicit operator ModInt(long n) { n %= MOD; if (n < 0) n += MOD; return new ModInt(n); } public ModInt Inverse() => Inverse(this, MOD); public static ModInt Inverse(ModInt x) => Inverse(x.num, MOD); public static long Inverse(long x, long m) { if (x % m == 0) throw new DivideByZeroException(); long a = x, b = m, u = 1, v = 0; while (b > 0) { long t = a / b; a -= t * b; long p = a; a = b; b = p; // swap(a, b); u -= t * v; p = u; u = v; v = p; // swap(u, v); } u %= m; if (u < 0) u += m; return u; } public static ModInt Pow(long x, long n) { long now = 1; for (n %= MOD - 1; n > 0; n /= 2, x = x * x % MOD) { if (n % 2 == 1) now = now * x % MOD; } return new ModInt(now); } public int CompareTo(ModInt x) { if (num == x.num) return 0; if (num > x.num) return 1; return -1; } public bool Equals(ModInt x) => num == x.num; public override bool Equals(object obj) => obj is ModInt m && num == m.num; public override int GetHashCode() { return HashCode.Combine(num); } } class Scanner { string[] s; int i; char[] separator = new char[] { ' ' }; public Scanner() { s = new string[0]; i = 0; } public string Read() => ReadString(); public string ReadString() { if (i < s.Length) return s[i++]; string st = Console.ReadLine(); while (st == "") st = Console.ReadLine(); s = st.Split(separator, StringSplitOptions.RemoveEmptyEntries); if (s.Length == 0) return ReadString(); i = 0; return s[i++]; } public string[] ReadStringArray(int N) { string[] Array = new string[N]; for (int i = 0; i < N; i++) { Array[i] = ReadString(); } return Array; } public int ReadInt() { return int.Parse(ReadString()); } public int[] ReadIntArray(int N, int add = 0) { int[] Array = new int[N]; for (int i = 0; i < N; i++) { Array[i] = ReadInt() + add; } return Array; } public long ReadLong() { return long.Parse(ReadString()); } public long[] ReadLongArray(int N, long add = 0) { long[] Array = new long[N]; for (int i = 0; i < N; i++) { Array[i] = ReadLong() + add; } return Array; } public double ReadDouble() { return double.Parse(ReadString()); } public double[] ReadDoubleArray(int N, double add = 0) { double[] Array = new double[N]; for (int i = 0; i < N; i++) { Array[i] = ReadDouble() + add; } return Array; } public T1 ReadValue() => (T1)Convert.ChangeType(ReadString(), typeof(T1)); public (T1, T2) ReadValue() { var inputs = ReadStringArray(2); var v1 = (T1)Convert.ChangeType(inputs[0], typeof(T1)); var v2 = (T2)Convert.ChangeType(inputs[1], typeof(T2)); return (v1, v2); } public (T1, T2, T3) ReadValue() { var inputs = ReadStringArray(3); var v1 = (T1)Convert.ChangeType(inputs[0], typeof(T1)); var v2 = (T2)Convert.ChangeType(inputs[1], typeof(T2)); var v3 = (T3)Convert.ChangeType(inputs[2], typeof(T3)); return (v1, v2, v3); } public (T1, T2, T3, T4) ReadValue() { var inputs = ReadStringArray(4); var v1 = (T1)Convert.ChangeType(inputs[0], typeof(T1)); var v2 = (T2)Convert.ChangeType(inputs[1], typeof(T2)); var v3 = (T3)Convert.ChangeType(inputs[2], typeof(T3)); var v4 = (T4)Convert.ChangeType(inputs[3], typeof(T4)); return (v1, v2, v3, v4); } public (T1, T2, T3, T4, T5) ReadValue() { var inputs = ReadStringArray(5); var v1 = (T1)Convert.ChangeType(inputs[0], typeof(T1)); var v2 = (T2)Convert.ChangeType(inputs[1], typeof(T2)); var v3 = (T3)Convert.ChangeType(inputs[2], typeof(T3)); var v4 = (T4)Convert.ChangeType(inputs[3], typeof(T4)); var v5 = (T5)Convert.ChangeType(inputs[4], typeof(T5)); return (v1, v2, v3, v4, v5); } public (T1, T2, T3, T4, T5, T6) ReadValue() { var inputs = ReadStringArray(6); var v1 = (T1)Convert.ChangeType(inputs[0], typeof(T1)); var v2 = (T2)Convert.ChangeType(inputs[1], typeof(T2)); var v3 = (T3)Convert.ChangeType(inputs[2], typeof(T3)); var v4 = (T4)Convert.ChangeType(inputs[3], typeof(T4)); var v5 = (T5)Convert.ChangeType(inputs[4], typeof(T5)); var v6 = (T6)Convert.ChangeType(inputs[5], typeof(T6)); return (v1, v2, v3, v4, v5, v6); } public (T1, T2, T3, T4, T5, T6, T7) ReadValue() { var inputs = ReadStringArray(7); var v1 = (T1)Convert.ChangeType(inputs[0], typeof(T1)); var v2 = (T2)Convert.ChangeType(inputs[1], typeof(T2)); var v3 = (T3)Convert.ChangeType(inputs[2], typeof(T3)); var v4 = (T4)Convert.ChangeType(inputs[3], typeof(T4)); var v5 = (T5)Convert.ChangeType(inputs[4], typeof(T5)); var v6 = (T6)Convert.ChangeType(inputs[5], typeof(T6)); var v7 = (T7)Convert.ChangeType(inputs[6], typeof(T7)); return (v1, v2, v3, v4, v5, v6, v7); } public T1[] ReadValueArray(int N) { var v1 = new T1[N]; for (int i = 0; i < N; i++) { v1[i] = ReadValue(); } return v1; } public (T1[], T2[]) ReadValueArray(int N) { var (v1, v2) = (new T1[N], new T2[N]); for (int i = 0; i < N; i++) { var (t1, t2) = ReadValue(); v1[i] = t1; v2[i] = t2; } return (v1, v2); } public (T1[], T2[], T3[]) ReadValueArray(int N) { var (v1, v2, v3) = (new T1[N], new T2[N], new T3[N]); for (int i = 0; i < N; i++) { var (t1, t2, t3) = ReadValue(); v1[i] = t1; v2[i] = t2; v3[i] = t3; } return (v1, v2, v3); } public (T1[], T2[], T3[], T4[]) ReadValueArray(int N) { var (v1, v2, v3, v4) = (new T1[N], new T2[N], new T3[N], new T4[N]); for (int i = 0; i < N; i++) { var (t1, t2, t3, t4) = ReadValue(); v1[i] = t1; v2[i] = t2; v3[i] = t3; v4[i] = t4; } return (v1, v2, v3, v4); } public (T1[], T2[], T3[], T4[], T5[]) ReadValueArray(int N) { var (v1, v2, v3, v4, v5) = (new T1[N], new T2[N], new T3[N], new T4[N], new T5[N]); for (int i = 0; i < N; i++) { var (t1, t2, t3, t4, t5) = ReadValue(); v1[i] = t1; v2[i] = t2; v3[i] = t3; v4[i] = t4; v5[i] = t5; } return (v1, v2, v3, v4, v5); } public (T1[], T2[], T3[], T4[], T5[], T6[]) ReadValueArray(int N) { var (v1, v2, v3, v4, v5, v6) = (new T1[N], new T2[N], new T3[N], new T4[N], new T5[N], new T6[N]); for (int i = 0; i < N; i++) { var (t1, t2, t3, t4, t5, t6) = ReadValue(); v1[i] = t1; v2[i] = t2; v3[i] = t3; v4[i] = t4; v5[i] = t5; v6[i] = t6; } return (v1, v2, v3, v4, v5, v6); } public (T1[], T2[], T3[], T4[], T5[], T6[], T7[]) ReadValueArray(int N) { var (v1, v2, v3, v4, v5, v6, v7) = (new T1[N], new T2[N], new T3[N], new T4[N], new T5[N], new T6[N], new T7[N]); for (int i = 0; i < N; i++) { var (t1, t2, t3, t4, t5, t6, t7) = ReadValue(); v1[i] = t1; v2[i] = t2; v3[i] = t3; v4[i] = t4; v5[i] = t5; v6[i] = t6; v7[i] = t7; } return (v1, v2, v3, v4, v5, v6, v7); } } }