// ReSharper disable ArrangeTypeMemberModifiers
// ReSharper disable ConvertIfStatementToSwitchStatement
// ReSharper disable FunctionRecursiveOnAllPaths
// ReSharper disable InconsistentNaming
// ReSharper disable InlineOutVariableDeclaration
// ReSharper disable InvertIf
// ReSharper disable JoinDeclarationAndInitializer
// ReSharper disable MemberCanBeMadeStatic.Global
// ReSharper disable MemberCanBeMadeStatic.Local
// ReSharper disable NonReadonlyMemberInGetHashCode
// ReSharper disable PossibleNullReferenceException
// ReSharper disable RedundantUsingDirective
// ReSharper disable SuggestVarOrType_BuiltInTypes
// ReSharper disable SuggestVarOrType_Elsewhere
// ReSharper disable TailRecursiveCall
// ReSharper disable UnusedMember.Global
// ReSharper disable UnusedMember.Local
// ReSharper disable UseObjectOrCollectionInitializert

#if true && UTAKA_LOCAL

//#if false
#define UTAKA_DEBUG
#endif

//#define TOPCODER

using System;
using System.Collections;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Runtime.CompilerServices;
using System.Text;
using System.Numerics;
using System.Runtime.InteropServices;
using System.Security.Cryptography;
using static UtakaApp.Util;

namespace UtakaApp
{
    public partial class Program
    {
        /*
        https://atcoder.jp/contests/abc148/tasks/abc148_e
        */
        
        // 解法

        public const string SiteName    = "AtCoder";
        public const string ContestName = "abc148";
        public const string ProblemName = "F";

        public static int u;
        public static int v;

        public List<int>[] to;
        public int         N;

        public int[] dist;

        public void Solve()
        {
            N = cin.ReadInt;

            to = new List<int>[N];
            for (int i = 0; i < N; i++)
            {
                to[i] = new List<int>();
            }

            int s = cin.ReadInt - 1;
            int t = cin.ReadInt - 1;

            for (int i = 0; i < N - 1; i++)
            {
                int a = cin.ReadInt - 1;
                int b = cin.ReadInt - 1;
                to[a].Add(b);
                to[b].Add(a);
            }

            int[] distS = CalcDist(s);
            int[] distT = CalcDist(t);

            int mx = 0;
            for (int i = 0; i < N; i++)
            {
                if (distS[i] < distT[i])
                {
                    mx = Math.Max(mx, distT[i]);
                }
            }

            int ans = mx - 1;
            cou.WriteLine(ans);
        }

        /// <summary>
        /// 頂点sからの各頂点への距離を求める
        /// </summary>
        public int[] CalcDist(int s)
        {
            dist = new int[N];
            Dfs(s);
            return dist;
        }

        public void Dfs(int v, int d = 0, int p = -1)
        {
            dist[v] = d;
            foreach (int u in to[v])
            {
                if (u == p) continue;
                Dfs(u, d + 1, v);
            }
        }

        public void Solve2()
        {
            int N = cin.ReadInt;
            u = cin.ReadInt - 1;
            v = cin.ReadInt - 1;

            LowestCommonAncestor lca = new LowestCommonAncestor(N);


            int[] A = new int[N - 1];
            int[] B = new int[N - 1];

            for (int i = 0; i < N - 1; i++)
            {
                A[i] = cin.ReadInt - 1;
                B[i] = cin.ReadInt - 1;

                lca.AddEdge(A[i], B[i]);
            }

            // 青木くんがroot
            lca.Build(root: v);

            int dist = lca.GetDistance(u, v);

            int dist2 = dist % 2 == 0 ? dist / 2 : dist / 2 + 1;

            // if (dist2 == 0)
            // {
            //     Dbg.WriteLine("!!!!!!!!!!!!!dist == 0");
            //     cou.WriteLine(dist);
            //     return;
            // }

            if (u == v)
            {
                cou.WriteLine(0);
                return;
            }

            if (dist == 1)
            {
                if (lca.G[u].Count == 1)
                {
                    // Dbg.WriteLine("!!!!!!!!!!!!逃げ場なし");
                    cou.WriteLine(0);
                    return;
                }
            }

            if (dist == 2)
            {
                if (lca.G[u].Count == 1)
                {
                    cou.WriteLine(1);
                    return;
                }
            }

            int ind1 = lca.pathIndexes[dist2 - 1];
            int ind2 = lca.pathIndexes[dist2];


            var lca2 = new LowestCommonAncestor(N);

            for (int i = 0; i < N - 1; i++)
            {
                if ((A[i] == ind1 && B[i] == ind2) || (A[i] == ind2 && B[i] == ind1))
                {
                    continue;
                }

                lca2.AddEdge(A[i], B[i]);
            }

            lca2.Build(root: ind2);

            int ans = lca2.depth.Max();

            ans += dist2;

            ans--;

            cou.WriteLine(ans);
        }
    }


    /// <summary>
    /// 最小共通祖先を求める
    /// </summary>
    public class LowestCommonAncestor
    {
        public int N;

        public List<int>[] G;

        public int[] vs;    // オイラーツアーの配列 長さは 2 * N - 1
        public int[] depth; // オイラーツアーの配列のノードの深さ 長さは 2 * N - 1

        public int[] id;               // 最初にそのノードを訪れたときにvs[]にメモしたインデックス 長さは N
        public int[] depthByInitIndex; // もともとのノード配列のインデックスから深さを求めるための配列 長さは N

        public SegTreeForLca segTreeForLca;

        public int[] pathIndexes;
        public bool  found;

        public LowestCommonAncestor(int N)
        {
            this.N = N;

            G = new List<int>[N];

            for (int i = 0; i < N; i++)
            {
                G[i] = new List<int>();
            }

            pathIndexes = new int[N];
            for (int i = 0; i < N; i++)
            {
                pathIndexes[i] = -1;
            }
        }

        public void AddEdge(int a, int b)
        {
            G[a].Add(b);
            G[b].Add(a);
        }

        public void Build(int root)
        {
            vs    = new int[2 * N - 1];
            depth = new int[2 * N - 1];
            id    = new int[N];

            int k = 0;

            Dfs(root, -1, 0, ref k);

            segTreeForLca = new SegTreeForLca(depth);

            depthByInitIndex = new int[N];
            for (int i = 0; i < 2 * N - 1; i++)
            {
                depthByInitIndex[vs[i]] = depth[i];
            }
        }

        /// <summary>
        /// ノードuとノードvの最小共通祖先のノードのインデックスを得る
        /// ここでいうインデックスは、元の配列のインデックスであり、オイラーツアーの方ではないので注意
        /// </summary>
        public int GetLcaIndex(int u, int v)
        {
            int left  = Math.Min(id[u], id[v]);
            int right = Math.Max(id[u], id[v]);

            int eulerIndex = segTreeForLca.QueryWithIndex(left, right + 1).Index;

            return vs[eulerIndex];
        }

        /// <summary>
        /// ノードuとノードvの距離を求める
        /// </summary>
        public int GetDistance(int u, int v)
        {
            int lcaIndex = GetLcaIndex(u, v);
            return depthByInitIndex[u] + depthByInitIndex[v] - 2 * depthByInitIndex[lcaIndex];
        }

        public void Dfs(int v, int parent, int d, ref int k)
        {
            if (!found)
            {
                pathIndexes[d] = v;

                if (v == Program.u)
                {
                    found = true;
                }
            }

            id[v]      = k;
            vs[k]      = v;
            depth[k++] = d;

            for (int i = 0; i < G[v].Count; i++)
            {
                if (G[v][i] != parent)
                {
                    Dfs(G[v][i], v, d + 1, ref k);
                    vs[k]      = v;
                    depth[k++] = d;

                    if (!found)
                    {
                        pathIndexes[d] = v;
                    }
                }
            }
        }
    }

    /// <summary>
    /// 
    /// SegmentTree LCA用
    /// QueryでIndexを取得できるタイプ
    /// 
    /// Dataは0始まりになっている
    /// ノードiの子ノードの番号は 2 * i + 1 / 2 * i + 2
    /// ノードiの親ノードの番号は (i - 1) / 2
    /// 
    ///        0
    ///    1       2
    ///  3   4   5   6
    /// 
    /// </summary>
    public class SegTreeForLca
    {
        private int   leafCount; // 葉の数
        private int[] data;

        private const int identity = int.MaxValue; // 単位元

        private int[] leafIndexes; // そのノードが採用している値の葉のindex

        public SegTreeForLca(IList<int> initialValues)
        {
            int initialValuesLength = initialValues.Count;

            leafCount = 1;

            while (leafCount < initialValuesLength) leafCount <<= 1;

            data        = new int[2 * leafCount - 1];
            leafIndexes = new int[2 * leafCount - 1];

            for (int i = 0; i < initialValuesLength; i++)
            {
                data[i + leafCount - 1]        = initialValues[i];
                leafIndexes[i + leafCount - 1] = i;
            }

            for (int i = initialValuesLength; i < leafCount; i++)
            {
                data[i + leafCount - 1]        = identity;
                leafIndexes[i + leafCount - 1] = i;
            }

            for (int i = leafCount - 2; i >= 0; i--)
            {
                if (data[i * 2 + 1] < data[i * 2 + 2])
                {
                    data[i]        = data[i * 2 + 1];
                    leafIndexes[i] = leafIndexes[i * 2 + 1];
                }
                else
                {
                    data[i]        = data[i * 2 + 2];
                    leafIndexes[i] = leafIndexes[i * 2 + 2];
                }
            }
        }

        /// <summary>
        /// ツリーの更新なしに i番目の葉の値を更新する
        /// </summary>
        public void AssignWithoutUpdate(int i, int value)
        {
            data[i + leafCount - 1] = value;
        }

        /// <summary>
        /// i番目の葉の値を更新し、ツリーを更新する
        /// </summary>
        public void Update(int i, int value)
        {
            int now = i + leafCount - 1;
            data[now] = value;

            while (now > 0)
            {
                now = (now - 1) / 2;

                if (data[now * 2 + 1] < data[now * 2 + 2])
                {
                    data[now]        = data[now * 2 + 1];
                    leafIndexes[now] = leafIndexes[now * 2 + 1];
                }
                else
                {
                    data[now]        = data[now * 2 + 2];
                    leafIndexes[now] = leafIndexes[now * 2 + 2];
                }
            }
        }

        /// <summary>
        /// i番目の葉の値を取得する
        /// </summary>
        public int Look(int i)
        {
            return data[i + leafCount - 1];
        }

        // QueryでIndexを取得したいときに使う
        public struct SegNodePair
        {
            public int Data;
            public int Index;

            public SegNodePair(int data, int index)
            {
                Data  = data;
                Index = index;
            }
        }

        public SegNodePair QueryWithIndex(int a, int b)
        {
            return QueryWithIndexInternal(a, b, 0, 0, leafCount);
        }

        /// <summary>
        /// [a, b) の区間に対するクエリについて
        /// ノード i (区間 [l, r) 担当) が答える
        /// </summary>
        private SegNodePair QueryWithIndexInternal(int a, int b, int i, int l, int r)
        {
            if (r <= a || b <= l) return new SegNodePair(identity, -1);
            if (a <= l && r <= b) return new SegNodePair(data[i], leafIndexes[i]);

            SegNodePair leftPair = QueryWithIndexInternal(a, b, i * 2 + 1,
                l, (l + r) / 2);
            SegNodePair rightPair = QueryWithIndexInternal(a, b, i * 2 + 2,
                (l + r) / 2, r);

            if (leftPair.Data < rightPair.Data)
            {
                return leftPair;
            }
            else
            {
                return rightPair;
            }
        }
    }

//=========================================================================================
// Debug IO
//=========================================================================================

    public partial class Program
    {
        //=========================================================================================
        // Main
        //=========================================================================================

        private readonly ConsoleInput cin;
        private readonly IConsole     cou;

        public Program(ConsoleInput cin, IConsole cou)
        {
            this.cin = cin;
            this.cou = cou;
        }

#if !TOPCODER
        public static void Main(string[] args)
        {
#if UTAKA_LOCAL
//#if false
            new TestCaseCheckerForAtCoder().TestProblems();
#else
            var cin = new ConsoleInput(System.Console.In);
            var console = new MyConsole();
            new Program(cin, console).Solve();
            console.Flush();
#endif
        }
#endif

        public void WriteEnumerable<T>(IEnumerable<T> A, string delimiter = " ")
        {
            if (!A.Any())
            {
                return;
            }

            var sb = new StringBuilder();
            foreach (T v in A)
            {
                sb.Append(v);
                sb.Append(delimiter);
            }

            if (sb.Length > 0)
            {
                sb.Length--;
            }

            cou.WriteLine(sb.ToString());
        }
    }

    public static class Util
    {
        public static int LowerBound<T>(T[] arr, int start, int end, T value, IComparer<T> comparer)
        {
            int low  = start;
            int high = end;
            while (low < high)
            {
                var mid = ((high - low) >> 1) + low;
                if (comparer.Compare(arr[mid], value) < 0)
                    low = mid + 1;
                else
                    high = mid;
            }

            return low;
        }

        public static int LowerBound<T>(T[] arr, T value) where T : IComparable
        {
            return LowerBound(arr, 0, arr.Length, value, Comparer<T>.Default);
        }

        public static int UpperBound<T>(T[] arr, int start, int end, T value, IComparer<T> comparer)
        {
            int low  = start;
            int high = end;
            while (low < high)
            {
                var mid = ((high - low) >> 1) + low;
                if (comparer.Compare(arr[mid], value) <= 0)
                    low = mid + 1;
                else
                    high = mid;
            }

            return low;
        }

        public static int UpperBound<T>(T[] arr, T value)
        {
            return UpperBound(arr, 0, arr.Length, value, Comparer<T>.Default);
        }

        public static int UpperBound<T>(List<T> list, int start, int end, T value, IComparer<T> comparer)
        {
            int low  = start;
            int high = end;
            while (low < high)
            {
                var mid = ((high - low) >> 1) + low;
                if (comparer.Compare(list[mid], value) <= 0)
                    low = mid + 1;
                else
                    high = mid;
            }

            return low;
        }

        public static int UpperBound<T>(List<T> list, T value)
        {
            return UpperBound(list, 0, list.Count, value, Comparer<T>.Default);
        }

        public static T[] Array1D<T>(int a, T defaultValue)
            where T : struct
        {
            var ret = new T[a];
            for (int i = 0; i < a; i++)
            {
                ret[i] = defaultValue;
            }

            return ret;
        }

        public static T[] Array1D<T>(int a)
            where T : struct
        {
            var ret = new T[a];
            return ret;
        }

        /// <summary>
        /// 要素数 (a, b) の、defaultValue で満たされた配列を作成します。
        /// </summary>
        /// <typeparam name="T">配列の型</typeparam>
        /// <param name="a">1次元の要素数</param>
        /// <param name="b">2次元の要素数</param>
        /// <param name="defaultValue">デフォルト値</param>
        /// <returns>指定した条件で初期化された配列</returns>
        public static T[,] Array2D<T>(int a, int b, T defaultValue)
            where T : struct
        {
            var ret = new T[a, b];
            for (int i = 0; i < a; i++)
            {
                for (int j = 0; j < b; j++)
                {
                    ret[i, j] = defaultValue;
                }
            }

            return ret;
        }

        public static T[,,] Array3D<T>(int a, int b, int c, T defaultValue)
            where T : struct
        {
            T[,,] ret = new T[a, b, c];

            for (int i = 0; i < a; i++)
            {
                for (int j = 0; j < b; j++)
                {
                    for (int k = 0; k < c; k++)
                    {
                        ret[i, j, k] = defaultValue;
                    }
                }
            }

            return ret;
        }

        /// <summary>
        /// 要素数 (a, b) の、defaultValue で満たされたJag配列を作成します。
        /// </summary>
        /// <typeparam name="T">配列の型</typeparam>
        /// <param name="a">1次元の要素数</param>
        /// <param name="b">2次元の要素数</param>
        /// <param name="defaultValue">デフォルト値</param>
        /// <returns>指定した条件で初期化された配列</returns>
        public static T[][] JagArray2D<T>(int a, int b, T defaultValue)
            where T : struct
        {
            var ret = new T[a][];
            for (int i = 0; i < a; i++)
            {
                var row = new T[b];
                ret[i] = row;

                for (int j = 0; j < b; j++)
                {
                    row[j] = defaultValue;
                }
            }

            return ret;
        }

        /// <summary>
        /// 要素数 (a, b) のdefault値で満たされたJag配列を作成します。
        /// </summary>
        /// <typeparam name="T">配列の型</typeparam>
        /// <param name="a">1次元の要素数</param>
        /// <param name="b">2次元の要素数</param>
        /// <returns>初期化された配列</returns>
        public static T[][] JagArray2D<T>(int a, int b)
            where T : struct
        {
            var ret = new T[a][];
            for (int i = 0; i < a; i++)
            {
                ret[i] = new T[b];
            }

            return ret;
        }

        public static T[][][] JagArray3D<T>(int a, int b, int c, T defaultValue)
            where T : struct
        {
            var ret = new T[a][][];
            for (int i = 0; i < a; i++)
            {
                T[][] aRow = new T[b][];
                ret[i] = aRow;

                for (int j = 0; j < b; j++)
                {
                    T[] bRow = new T[c];
                    aRow[j] = bRow;

                    for (int k = 0; k < c; k++)
                    {
                        bRow[k] = defaultValue;
                    }
                }
            }

            return ret;
        }

        public static T[][][] JagArray3D<T>(int a, int b, int c)
            where T : struct
        {
            var ret = new T[a][][];
            for (int i = 0; i < a; i++)
            {
                T[][] aRow = new T[b][];
                ret[i] = aRow;

                for (int j = 0; j < b; j++)
                {
                    T[] bRow = new T[c];
                    aRow[j] = bRow;
                }
            }

            return ret;
        }

        public static T[][][][] JagArray4D<T>(int a, int b, int c, int d, T defaultValue)
            where T : struct
        {
            var ret = new T[a][][][];
            for (int i = 0; i < a; i++)
            {
                T[][][] aRow = new T[b][][];
                ret[i] = aRow;

                for (int j = 0; j < b; j++)
                {
                    T[][] bRow = new T[c][];
                    aRow[j] = bRow;

                    for (int k = 0; k < c; k++)
                    {
                        T[] cRow = new T[d];
                        bRow[k] = cRow;

                        for (int l = 0; l < d; l++)
                        {
                            cRow[l] = defaultValue;
                        }
                    }
                }
            }

            return ret;
        }

        public static T[][][][] JagArray4D<T>(int a, int b, int c, int d)
            where T : struct
        {
            var ret = new T[a][][][];
            for (int i = 0; i < a; i++)
            {
                T[][][] aRow = new T[b][][];
                ret[i] = aRow;

                for (int j = 0; j < b; j++)
                {
                    T[][] bRow = new T[c][];
                    aRow[j] = bRow;

                    for (int k = 0; k < c; k++)
                    {
                        T[] cRow = new T[d];
                        bRow[k] = cRow;
                    }
                }
            }

            return ret;
        }

        public static T[][][][][] JagArray5D<T>(int a, int b, int c, int d, int e, T defaultValue)
            where T : struct
        {
            var ret = new T[a][][][][];
            for (int i = 0; i < a; i++)
            {
                T[][][][] aRow = new T[b][][][];
                ret[i] = aRow;

                for (int j = 0; j < b; j++)
                {
                    T[][][] bRow = new T[c][][];
                    aRow[j] = bRow;

                    for (int k = 0; k < c; k++)
                    {
                        T[][] cRow = new T[d][];
                        bRow[k] = cRow;

                        for (int l = 0; l < d; l++)
                        {
                            T[] dRow = new T[e];
                            cRow[l] = dRow;

                            for (int m = 0; m < e; m++)
                            {
                                dRow[m] = defaultValue;
                            }
                        }
                    }
                }
            }

            return ret;
        }

        public static T[][][][][] JagArray5D<T>(int a, int b, int c, int d, int e)
            where T : struct
        {
            var ret = new T[a][][][][];
            for (int i = 0; i < a; i++)
            {
                T[][][][] aRow = new T[b][][][];
                ret[i] = aRow;

                for (int j = 0; j < b; j++)
                {
                    T[][][] bRow = new T[c][][];
                    aRow[j] = bRow;

                    for (int k = 0; k < c; k++)
                    {
                        T[][] cRow = new T[d][];
                        bRow[k] = cRow;

                        for (int l = 0; l < d; l++)
                        {
                            T[] dRow = new T[e];
                            cRow[l] = dRow;
                        }
                    }
                }
            }

            return ret;
        }

        /// <summary>
        /// ジャグ配列をコピーして返す。
        /// </summary>
        public static T[][] CopyJagArray2D<T>(T[][] source)
            where T : struct
        {
            int   len  = source.Length;
            T[][] dest = new T[len][];

            for (int i = 0; i < len; i++)
            {
                T[] inner       = source[i];
                int innerLength = inner.Length;
                T[] newer       = new T[innerLength];
                Array.Copy(inner, newer, innerLength);
                dest[i] = newer;
            }

            return dest;
        }
    }

    public static class UtakaExtentions
    {
        /// <summary>
        /// IList<T>をコピーします
        /// </summary>
        public static T[] Copy<T>(this IList<T> a)
        {
            T[] ret = new T[a.Count];

            for (int i = 0; i < a.Count; i++) ret[i] = a[i];

            return ret;
        }

        /// <summary>
        /// 2次元ジャグ配列をコピーして返す。
        /// </summary>
        public static T[][] Copy<T>(this T[][] source)
            where T : struct
        {
            int   len  = source.Length;
            T[][] dest = new T[len][];

            for (int i = 0; i < len; i++)
            {
                T[] inner       = source[i];
                int innerLength = inner.Length;
                T[] newer       = new T[innerLength];
                Array.Copy(inner, newer, innerLength);
                dest[i] = newer;
            }

            return dest;
        }
    }

    public class IntLargeComparer : IComparer<int>
    {
        public static IntLargeComparer Instance = new IntLargeComparer();

        public int Compare(int x, int y)
        {
            return y - x;
        }
    }

    public class LongLargeComparer : IComparer<long>
    {
        public static LongLargeComparer Instance = new LongLargeComparer();

        public int Compare(long x, long y)
        {
            if (x > y) return -1;
            if (x < y) return 1;
            return 0;
        }
    }

    public class ConsoleInput
    {
        private readonly char          _separator = ' ';
        private readonly TextReader    _stream;
        private readonly Queue<string> inputStream;

        public ConsoleInput(TextReader stream, char separator = ' ')
        {
            _separator  = separator;
            _stream     = stream;
            inputStream = new Queue<string>();
        }

        public string Read
        {
            get
            {
                if (inputStream.Count != 0)
                {
                    return inputStream.Dequeue();
                }

                var tmp = _stream.ReadLine().Split(_separator);
                for (var i = 0; i < tmp.Length; ++i)
                {
                    inputStream.Enqueue(tmp[i]);
                }

                return inputStream.Dequeue();
            }
        }

        public string ReadLine   => _stream.ReadLine();
        public int    ReadInt    => int.Parse(Read);
        public long   ReadLong   => long.Parse(Read);
        public double ReadDouble => double.Parse(Read);

        public string[] ReadStrArray(long N)
        {
            var ret = new string[N];
            for (long i = 0; i < N; ++i)
            {
                ret[i] = Read;
            }

            return ret;
        }

        public int[] ReadIntArray(long N)
        {
            var ret = new int[N];
            for (long i = 0; i < N; ++i)
            {
                ret[i] = ReadInt;
            }

            return ret;
        }

        public int[] ReadIntArrayMinus1(long N)
        {
            var ret = new int[N];
            for (long i = 0; i < N; ++i)
            {
                ret[i] = ReadInt - 1;
            }

            return ret;
        }

        public long[] ReadLongArray(long N)
        {
            var ret = new long[N];
            for (long i = 0; i < N; ++i)
            {
                ret[i] = ReadLong;
            }

            return ret;
        }
    }

    public interface IConsole
    {
        void Flush();
        void Write(object obj);
        void Write(string str);
        void WriteLine(object obj);
        void WriteLine(string str);
        void WriteLine();
    }

    public class MyConsole : IConsole
    {
        public MyConsole()
        {
            var sw = new StreamWriter(Console.OpenStandardOutput()) {AutoFlush = false};
            Console.SetOut(sw);
        }

        public void Flush()
        {
            Console.Out.Flush();
        }

        public void Write(object obj)
        {
            Write(obj.ToString());
        }

        public void Write(string str)
        {
            Console.Write(str);
        }

        public void WriteLine(object obj)
        {
            WriteLine(obj.ToString());
        }

        public void WriteLine(string str)
        {
            Console.WriteLine(str);
        }

        public void WriteLine()
        {
            Console.WriteLine();
        }
    }

#if UTAKA_LOCAL

    public class DebugConsole : IConsole
    {
        private readonly StringBuilder mSb;

        public DebugConsole()
        {
            mSb = new StringBuilder();
        }

        public void Flush()
        {
            // 何もしない
        }

        public void Write(object obj)
        {
            Write(obj.ToString());
        }

        public void Write(string str)
        {
            mSb.Append(str);
        }

        public void WriteLine(object obj)
        {
            WriteLine(obj.ToString());
        }

        public void WriteLine(string str)
        {
            mSb.AppendLine(str);
        }

        public void WriteLine()
        {
            mSb.AppendLine();
        }

        public string GetAllOutput()
        {
            return mSb.ToString();
        }
    }

#endif

#if UTAKA_LOCAL

    public class TestCaseCheckerForAtCoder
    {
        private string GetDirectoryPath()
        {
            var problemPart = string.IsNullOrEmpty(Program.ProblemName)
                ? ""
                : $"/{Program.ProblemName}";

            return
                $"{Environment.GetFolderPath(Environment.SpecialFolder.UserProfile)}/AlgorithmPrac/{Program.SiteName}/{Program.ContestName}{problemPart}";
        }

        private string GetInputFilePath(int testCaseNumber)
        {
            return $"{GetDirectoryPath()}/sample-{testCaseNumber}.in";
        }

        private string GetOutputFilePath(int testCaseNumber)
        {
            return $"{GetDirectoryPath()}/sample-{testCaseNumber}.out";
        }

        public bool TestProblem(int testCaseNumber)
        {
            var inputFilePath  = GetInputFilePath(testCaseNumber);
            var outputFilePath = GetOutputFilePath(testCaseNumber);

            TextReader inputStream = new StreamReader(inputFilePath);
            var        cin         = new ConsoleInput(inputStream);

            var debugConsoleWriter = new DebugConsole();

            new Program(cin, debugConsoleWriter).Solve();

            var output = debugConsoleWriter.GetAllOutput();

            TextReader outputStream = new StreamReader(outputFilePath);
            var        outputAnswer = outputStream.ReadToEnd();

            Dbg.WriteLine(output);
            Dbg.WriteLine(outputAnswer);

            var isCorrect = output == outputAnswer;

            return isCorrect;
        }

        public void TestProblems(int targetTestCaseNumber = -1)
        {
            if (targetTestCaseNumber >= 0)
            {
                Console.WriteLine($"!!!!!!!!!!!! Check TestCase {targetTestCaseNumber} !!!!!!!!!!");
            }

            bool isSuccessAll = true;

            int testCaseNumber = 0;
            while (true)
            {
                testCaseNumber++;

                bool foundTargetTest = targetTestCaseNumber == testCaseNumber;

                if (targetTestCaseNumber >= 0 && !foundTargetTest)
                {
                    continue;
                }

                var inputFileName = GetInputFilePath(testCaseNumber);
                if (!File.Exists(inputFileName))
                {
                    break;
                }

                Console.WriteLine($"TestCase {testCaseNumber} =====================================================");

                var result = TestProblem(testCaseNumber);

                if (result)
                {
                    Console.WriteLine("Success");
                }
                else
                {
                    isSuccessAll = false;
                    Console.WriteLine("Failure *****");
                }

                if (foundTargetTest)
                {
                    break;
                }
            }

            if (isSuccessAll)
            {
                Console.WriteLine("!!!!!!!!! All Success !!!!!!!!!");
            }
        }
    }

#endif

    public static class Dbg
    {
        [Conditional("UTAKA_DEBUG")]
        public static void WriteLine(string str)
        {
            Console.WriteLine(str);
        }

        [Conditional("UTAKA_DEBUG")]
        public static void WriteLine()
        {
            Console.WriteLine();
        }

        [Conditional("UTAKA_DEBUG")]
        public static void Write(string str)
        {
            Console.Write(str);
        }
    }
}


Measured memory_bytes: 36492