using System; using System.ComponentModel; using System.Collections; using System.Collections.Generic; using System.Diagnostics; using System.Diagnostics.Contracts; using System.IO; using System.Linq; using System.Numerics; using System.Runtime.CompilerServices; using System.Runtime.InteropServices; using System.Text; using static Functions; using ModInt = StaticModInt; static class Program { static public void Main(string[] args) { Console.SetOut(new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false }); new Solver(); Console.Out.Flush(); } } public class Solver { public Solver() { Solve(); } struct Op : IReRootingDPOperator { public int SIdentity => 0; public int TtoS(int t) => t; public int Merge(int x, int y) => x + y; public int AddRoot(int i, int j, int x) => x + 1; } void Solve() { int n = ri, q = ri; var g = new Graph(n); var dp = new ReRootingDP(n); for (int i = 0; i < n - 1; i++) { int a = ri - 1, b = ri - 1; g.AddEdge(a, b); dp.AddEdge(a, b); } var td = new TreeDoubling(g); var tj = new TreeJump(g); dp.Calc(); var ans = new List(); for (int i = 0; i < q; i++) { int s = ri - 1, t = ri - 1; var dist = td.Dist(s, t); if (dist % 2 == 1) { ans.Add(0); } else { int c = n; int m = tj.Jump(s, t, (int)dist / 2); c -= dp[tj.Jump(m, s, 1), m]; c -= dp[tj.Jump(m, t, 1), m]; ans.Add(c); } } WriteJoin("\n", ans); } const long INF = 1L << 60; int ri { get { return (int)sc.Integer(); } } long rl { get { return sc.Integer(); } } ulong rul { get { return sc.UInteger(); } } double rd { get { return sc.Double(); } } string rs { get { return sc.Scan(); } } string rline { get { return sc.Line(); } } public StreamScanner sc = new StreamScanner(Console.OpenStandardInput()); [MethodImpl(MethodImplOptions.AggressiveInlining)] T[] RepArray(T t, int count) => Enumerable.Repeat(t, count).ToArray(); [MethodImpl(MethodImplOptions.AggressiveInlining)] void WriteJoin(string s, IEnumerable t) => Console.WriteLine(string.Join(s, t)); [MethodImpl(MethodImplOptions.AggressiveInlining)] void WriteMat(T[,] a) { int sz1 = a.GetLength(0); int sz2 = a.GetLength(1); for (int i = 0; i < sz1; i++) { var s = new List(); for (int j = 0; j < sz2; j++) s.Add(a[i, j].ToString()); WriteJoin(" ", s); } } [MethodImpl(MethodImplOptions.AggressiveInlining)] void Write(object t) => Console.WriteLine(t.ToString()); [MethodImpl(MethodImplOptions.AggressiveInlining)] void Write(string str) => Console.WriteLine(str); [MethodImpl(MethodImplOptions.AggressiveInlining)] void Write(string str, object arg1) => Console.WriteLine(str, arg1); [MethodImpl(MethodImplOptions.AggressiveInlining)] void Write(string str, object arg1, object arg2) => Console.WriteLine(str, arg1, arg2); [MethodImpl(MethodImplOptions.AggressiveInlining)] void Write(string str, object arg1, object arg2, object arg3) => Console.WriteLine(str, arg1, arg2, arg3); [MethodImpl(MethodImplOptions.AggressiveInlining)] void Write(string str, params object[] arg) => Console.WriteLine(str, arg); [MethodImpl(MethodImplOptions.AggressiveInlining)] void WriteFlush(object t) { Console.WriteLine(t.ToString()); Console.Out.Flush(); } [MethodImpl(MethodImplOptions.AggressiveInlining)] void WriteError(object t) => Console.Error.WriteLine(t.ToString()); [MethodImpl(MethodImplOptions.AggressiveInlining)] void YN(bool t) => Console.WriteLine(t ? "YES" : "NO"); [MethodImpl(MethodImplOptions.AggressiveInlining)] void Yn(bool t) => Console.WriteLine(t ? "Yes" : "No"); [MethodImpl(MethodImplOptions.AggressiveInlining)] void yn(bool t) => Console.WriteLine(t ? "yes" : "no"); } public interface IStaticMod { uint Mod { get; } bool IsPrime { get; } } public readonly struct Mod1000000007 : IStaticMod { public uint Mod => 1000000007; public bool IsPrime => true; } public readonly struct Mod998244353 : IStaticMod { public uint Mod => 998244353; public bool IsPrime => true; } public readonly struct StaticModInt : IEquatable>, IFormattable where T : struct, IStaticMod { internal readonly uint _v; private static readonly T op = default; public int Value => (int)_v; public static int Mod => (int)op.Mod; public static StaticModInt Zero => default; public static StaticModInt One => new StaticModInt(1u); [MethodImpl(256)] public static StaticModInt Raw(int v) { var u = unchecked((uint)v); return new StaticModInt(u); } [MethodImpl(256)] public StaticModInt(long v) : this(Round(v)) { } [MethodImpl(256)] public StaticModInt(ulong v) : this((uint)(v % op.Mod)) { } [MethodImpl(256)] private StaticModInt(uint v) => _v = v; [MethodImpl(256)] private static uint Round(long v) { var x = v % op.Mod; if (x < 0) x += op.Mod; return (uint)x; } [MethodImpl(256)] public static StaticModInt operator ++(StaticModInt v) { var x = v._v + 1; if (x == op.Mod) x = 0; return new StaticModInt(x); } [MethodImpl(256)] public static StaticModInt operator --(StaticModInt v) { var x = v._v; if (x == 0) x = op.Mod; return new StaticModInt(x - 1); } [MethodImpl(256)] public static StaticModInt operator +(StaticModInt lhs, StaticModInt rhs) { var v = lhs._v + rhs._v; if (v >= op.Mod) v -= op.Mod; return new StaticModInt(v); } [MethodImpl(256)] public static StaticModInt operator -(StaticModInt lhs, StaticModInt rhs) { unchecked { var v = lhs._v - rhs._v; if (v >= op.Mod) v += op.Mod; return new StaticModInt(v); } } [MethodImpl(256)] public static StaticModInt operator *(StaticModInt lhs, StaticModInt rhs) => new StaticModInt((uint)((ulong)lhs._v * rhs._v % op.Mod)); [MethodImpl(256)] public static StaticModInt operator /(StaticModInt lhs, StaticModInt rhs) => lhs * rhs.Inv(); [MethodImpl(256)] public static StaticModInt operator +(StaticModInt v) => v; [MethodImpl(256)] public static StaticModInt operator -(StaticModInt v) => new StaticModInt(v._v == 0 ? 0 : op.Mod - v._v); [MethodImpl(256)] public static bool operator ==(StaticModInt lhs, StaticModInt rhs) => lhs._v == rhs._v; [MethodImpl(256)] public static bool operator !=(StaticModInt lhs, StaticModInt rhs) => lhs._v != rhs._v; [MethodImpl(256)] public static implicit operator StaticModInt(int v) => new StaticModInt(v); [MethodImpl(256)] public static implicit operator StaticModInt(uint v) => new StaticModInt((long)v); [MethodImpl(256)] public static implicit operator StaticModInt(long v) => new StaticModInt(v); [MethodImpl(256)] public static implicit operator StaticModInt(ulong v) => new StaticModInt(v); [MethodImpl(256)] public static implicit operator long(StaticModInt v) => v._v; [MethodImpl(256)] public static implicit operator ulong(StaticModInt v) => v._v; [MethodImpl(256)] public StaticModInt Pow(long n) { var x = this; var r = new StaticModInt(1U); while (n > 0) { if ((n & 1) > 0) r *= x; x *= x; n >>= 1; } return r; } [MethodImpl(256)] public StaticModInt Inv() { var (x, y, g) = ExtGcd(_v, op.Mod); return new StaticModInt(x); } [MethodImpl(256)] static (long x, long y, long g) ExtGcd(long a, long b) { if (b == 0) return a >= 0 ? (1, 0, a) : (-1, 0, -a); long c = SafeMod(a, b); var (x2, y2, g) = ExtGcd(b, c); long x = SafeMod(y2, b); long y = (g - a * x) / b; return (x, y, g); } [MethodImpl(256)] static long SafeMod(long x, long m) { long r = x % m; if (r < 0) r += m; return r; } [MethodImpl(256)] public override string ToString() => _v.ToString(); [MethodImpl(256)] public string ToString(string format, IFormatProvider formatProvider) => _v.ToString(format, formatProvider); [MethodImpl(256)] public override bool Equals(object obj) => obj is StaticModInt m && Equals(m); [MethodImpl(256)] public bool Equals(StaticModInt other) => _v == other._v; [MethodImpl(256)] public override int GetHashCode() => _v.GetHashCode(); } public static class Functions { public static int Popcount(ulong x) { x = (x & 0x5555555555555555UL) + ((x >> 1) & 0x5555555555555555UL); x = (x & 0x3333333333333333UL) + ((x >> 2) & 0x3333333333333333UL); x = (x & 0x0f0f0f0f0f0f0f0fUL) + ((x >> 4) & 0x0f0f0f0f0f0f0f0fUL); x = (x & 0x00ff00ff00ff00ffUL) + ((x >> 8) & 0x00ff00ff00ff00ffUL); x = (x & 0x0000ffff0000ffffUL) + ((x >> 16) & 0x0000ffff0000ffffUL); x = (x & 0x00000000ffffffffUL) + ((x >> 32) & 0x00000000ffffffffUL); return (int)x; } public static int Popcount(int x) { x = (x & 0x55555555) + ((x >> 1) & 0x55555555); x = (x & 0x33333333) + ((x >> 2) & 0x33333333); x = (x & 0x0f0f0f0f) + ((x >> 4) & 0x0f0f0f0f); x = (x & 0x00ff00ff) + ((x >> 8) & 0x00ff00ff); x = (x & 0x0000ffff) + ((x >> 16) & 0x0000ffff); return x; } public static int Ctz(long x) { if (x == 0) return -1; return Popcount((ulong)((x & -x) - 1)); } public static int SafeMod(int x, int m) { int r = x % m; return r < 0 ? r + m : r; } public static long SafeMod(long x, long m) { long r = x % m; return r < 0 ? r + m : r; } [MethodImpl(MethodImplOptions.AggressiveInlining)] public static int Sign(long x) => x == 0 ? 0 : (x < 0 ? -1 : 1); [MethodImpl(MethodImplOptions.AggressiveInlining)] public static int DigitSum(long n, int d = 10) { long s = 0; while (n > 0) { s += n % d; n /= d; } return (int)s; } [MethodImpl(MethodImplOptions.AggressiveInlining)] public static long Floor(long a, long b) => a >= 0 ? a / b : (a + 1) / b - 1; [MethodImpl(MethodImplOptions.AggressiveInlining)] public static long Ceil(long a, long b) => a > 0 ? (a - 1) / b + 1 : a / b; [MethodImpl(MethodImplOptions.AggressiveInlining)] public static int Gcd(int a, int b) => b == 0 ? a : Gcd(b, a % b); [MethodImpl(MethodImplOptions.AggressiveInlining)] public static long Gcd(long a, long b) => b == 0 ? a : Gcd(b, a % b); [MethodImpl(MethodImplOptions.AggressiveInlining)] public static void Swap(ref int x, ref int y) { x ^= y; y ^= x; x ^= y; } [MethodImpl(MethodImplOptions.AggressiveInlining)] public static void Swap(ref long x, ref long y) { x ^= y; y ^= x; x ^= y; } [MethodImpl(MethodImplOptions.AggressiveInlining)] public static void Swap(ref T x, ref T y) { T t = y; y = x; x = t; } [MethodImpl(MethodImplOptions.AggressiveInlining)] public static T Clamp(T x, T l, T r) where T : IComparable => x.CompareTo(l) <= 0 ? l : (x.CompareTo(r) <= 0 ? x : r); [MethodImpl(MethodImplOptions.AggressiveInlining)] public static T Clamp(ref T x, T l, T r) where T : IComparable => x = x.CompareTo(l) <= 0 ? l : (x.CompareTo(r) <= 0 ? x : r); [MethodImpl(MethodImplOptions.AggressiveInlining)] public static void Chmin(ref T x, T y) where T : IComparable { if (x.CompareTo(y) > 0) x = y; } [MethodImpl(MethodImplOptions.AggressiveInlining)] public static void Chmax(ref T x, T y) where T : IComparable { if (x.CompareTo(y) < 0) x = y; } public static int LowerBound(T[] arr, Func comp, int l = -1, int r = -1) => LowerBound(arr.AsSpan(), comp, l, r); public static int LowerBound(Span data, Func comp, int l = -1, int r = -1) { if (data.Length == 0) return -1; if (l == -1) l = 0; if (r == -1) r = data.Length; while (l < r) { int x = (l + r) / 2; if (comp(data[x]) < 0) l = x + 1; else r = x; } return l; } } public class StreamScanner { public StreamScanner(Stream stream) { str = stream; } private readonly Stream str; private readonly byte[] buf = new byte[1024]; private int len, ptr; public bool isEof = false; public bool IsEndOfStream { get { return isEof; } } private byte read() { if (isEof) throw new EndOfStreamException(); if (ptr >= len) { ptr = 0; if ((len = str.Read(buf, 0, 1024)) <= 0) { isEof = true; return 0; } } return buf[ptr++]; } public char Char() { byte b = 0; do b = read(); while (b < 33 || 126 < b); return (char)b; } public string Line() { var sb = new StringBuilder(); for (var b = Char(); b != 10 && !isEof; b = (char)read()) sb.Append(b); return sb.ToString(); } public string Scan() { var sb = new StringBuilder(); for (var b = Char(); b >= 33 && b <= 126; b = (char)read()) sb.Append(b); return sb.ToString(); } public long Integer() { long ret = 0; byte b = 0; var ng = false; do b = read(); while (b != '-' && (b < '0' || '9' < b)); if (b == '-') { ng = true; b = read(); } for (; true; b = read()) { if (b < '0' || '9' < b) return ng ? -ret : ret; else ret = ret * 10 + b - '0'; } } public ulong UInteger() { ulong ret = 0; byte b = 0; do b = read(); while (b < '0' || '9' < b); for (; true; b = read()) { if (b < '0' || '9' < b) return ret; else ret = ret * 10 + b - '0'; } } public double Double() { return double.Parse(Scan()); } } class Graph { public struct Edge { public int src, to; public long cost; public Edge(int _src, int _to, long _cost) { src = _src; to = _to; cost = _cost; } public Edge(int _to, long _cost) { src = -1; to = _to; cost = _cost; } } int n; public int Size => n; public List[] e; public Graph(List[] _g) { n = _g.Length; e = new List[n]; for (int i = 0; i < n; i++) e[i] = new List(); for (int i = 0; i < n; i++) foreach (var j in _g[i]) e[i].Add(new Edge(i, j, 1)); } public Graph(int _n) { n = _n; e = new List[n]; for (int i = 0; i < n; i++) e[i] = new List(); } public void AddEdge(int x, int y, long cost = 1) { e[x].Add(new Edge(x, y, cost)); e[y].Add(new Edge(y, x, cost)); } public void AddDirectedEdge(int src, int to, long cost = 1) { e[src].Add(new Edge(src, to, cost)); } } interface IReRootingDPOperator { S SIdentity { get; } S TtoS(T t); S Merge(S x, S y); T AddRoot(int i, int j, S x); } class ReRootingDP where Op : IReRootingDPOperator { int n; Op op = default; List[] edges; T[] ans; Dictionary[] dp; public T this[int i, int j] { get => dp[i][j]; } public T this[int i] { get => ans[i]; } public ReRootingDP(int _n) { n = _n; edges = new List[n]; for (int i = 0; i < n; i++) edges[i] = new List(); } public void AddEdge(int u, int v) { edges[u].Add(v); edges[v].Add(u); } public void Calc() { dp = new Dictionary[n]; for (int i = 0; i < n; i++) dp[i] = new Dictionary(); seen = new bool[n]; for (int i = 0; i < n; i++) if (!seen[i]) DFS1(i); seen = new bool[n]; for (int i = 0; i < n; i++) if (!seen[i]) DFS2(i); ans = new T[n]; for (int i = 0; i < n; i++) ans[i] = dp[i][-1]; } bool[] seen; private void DFS1(int x, int p = -1) { seen[x] = true; S val = op.SIdentity; foreach (var y in edges[x]) { if (y == p) continue; DFS1(y, x); val = op.Merge(val, op.TtoS(dp[y][x])); } dp[x].Add(p, op.AddRoot(x, p, val)); } private void DFS2(int x, int p = -1) { seen[x] = true; int deg = edges[x].Count; var dp_r = new S[deg + 1]; dp_r[deg] = op.SIdentity; for (int i = deg - 1; i >= 0; i--) dp_r[i] = op.Merge(dp_r[i + 1], op.TtoS(dp[edges[x][i]][x])); if (p != -1) dp[x].Add(-1, op.AddRoot(x, -1, dp_r[0])); S sum_l = op.SIdentity; for (int i = 0; i < deg; i++) { int y = edges[x][i]; if (y != p) { dp[x].Add(y, op.AddRoot(x, y, op.Merge(sum_l, dp_r[i + 1]))); DFS2(y, x); } sum_l = op.Merge(sum_l, op.TtoS(dp[edges[x][i]][x])); } } } class TreeDoubling { int n, log, root; int[] depth; long[] dist; int[,] par; public TreeDoubling(in Graph g, int _root = 0) { n = g.Size; root = _root; while ((1 << log) < n) log++; if (log <= 0) log = 1; depth = new int[n]; dist = new long[n]; par = new int[n, log]; for (int i = 0; i < n; i++) for (int j = 0; j < log; j++) par[i, j] = -1; var st = new Stack(); st.Push(root); while (st.Count > 0) { int x = st.Pop(); for (int j = 0; j < log - 1 && par[x, j] > -1; j++) par[x, j + 1] = par[par[x, j], j]; foreach (var y in g.e[x]) { if (y.to == par[x, 0]) continue; depth[y.to] = depth[x] + 1; dist[y.to] = dist[x] + y.cost; par[y.to, 0] = x; st.Push(y.to); } } } [MethodImpl(256)] public int LCA(int x, int y) { if (depth[x] > depth[y]) { x ^= y; y ^= x; x ^= y; } int diff = depth[y] - depth[x]; for (int i = 0; diff > 0; i++) { if ((diff & 1) == 1) y = par[y, i]; diff >>= 1; } if (x == y) return x; for (int i = log - 1; i >= 0; i--) { if (par[x, i] != par[y, i]) { x = par[x, i]; y = par[y, i]; } } return par[x, 0]; } [MethodImpl(256)] public long Dist(int x) => dist[x]; [MethodImpl(256)] public long Dist(int x, int y) => dist[x] + dist[y] - 2 * dist[LCA(x, y)]; [MethodImpl(256)] public bool OnPath(int x, int y, int a) => Dist(x, a) + Dist(a, y) == Dist(x, y); [MethodImpl(256)] public int Ancestor(int x, int k = 1) { if (depth[x] < k) return -1; for (int i = 0; i < log; i++) if (((k >> i) & 1) == 1) x = par[x, i]; return x; } } class TreeJump { int n, u, v; TreeDoubling du, dv; public TreeJump(in Graph g) { n = g.Size; u = 0; v = 0; var qu = new Queue<(int x, int p)>(); qu.Enqueue((0, -1)); while (qu.Count > 0) { var x = qu.Dequeue(); foreach (var e in g.e[x.x]) if (x.p != e.to) qu.Enqueue((e.to, x.x)); if (qu.Count == 0) u = x.x; } qu.Enqueue((u, -1)); while (qu.Count > 0) { var x = qu.Dequeue(); foreach (var e in g.e[x.x]) if (x.p != e.to) qu.Enqueue((e.to, x.x)); if (qu.Count == 0) v = x.x; } du = new TreeDoubling(g, u); dv = new TreeDoubling(g, v); } [MethodImpl(256)] public int Jump(int x, int k) { if (du.Dist(x) >= k) return du.Ancestor(x, k); if (dv.Dist(x) >= k) return dv.Ancestor(x, k); return -1; } [MethodImpl(256)] public int Jump(int x, int y, int k) { var d = du.Dist(x, y); if (d < k) return -1; return du.Dist(x, du.LCA(x, y)) >= k ? du.Ancestor(x, k) : du.Ancestor(y, (int)d - k); } }