Problem:
Score : 800 points

Problem Statement

Takahashi and Aoki will play a game on a tree.
The tree has N vertices numbered 1 to N, and the i-th of the N-1 edges connects Vertex a_i and Vertex b_i.

At the beginning of the game, each vertex contains a coin.
Starting from Takahashi, he and Aoki will alternately perform the following operation:

Choose a vertex v that contains one or more coins, and remove all the coins from v.

Then, move each coin remaining on the tree to the vertex that is nearest to v among the adjacent vertices of the coin's current vertex.

The player who becomes unable to play, loses the game.
That is, the player who takes his turn when there is no coin remaining on the tree, loses the game.
Determine the winner of the game when both players play optimally.

Constraints

1 \leq N \leq 2 \times 10^5

1 \leq a_i, b_i \leq N

a_i \neq b_i

The graph given as input is a tree.

Input

Input is given from Standard Input in the following format:

N
a_1 b_1
a_2 b_2
:
a_{N-1} b_{N-1}

Output

Print First if Takahashi will win, and print Second if Aoki will win.

Sample Input 1

3
1 2
2 3

Sample Output 1

First

Here is one possible progress of the game:

Takahashi removes the coin from Vertex 1. Now, Vertex 1 and Vertex 2 contain one coin each.

Aoki removes the coin from Vertex 2. Now, Vertex 2 contains one coin.

Takahashi removes the coin from Vertex 2. Now, there is no coin remaining on the tree.

Aoki takes his turn when there is no coin on the tree and loses.

Sample Input 2

6
1 2
2 3
2 4
4 6
5 6

Sample Output 2

Second

Sample Input 3

7
1 7
7 4
3 4
7 5
6 3
2 1

Sample Output 3

First

Solution in C# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using static Asakatsu20200322F.Input;

namespace Asakatsu20200322F
{
    static class Input
    {
        /// <summary>
        /// 1行の入力をTに応じてリストに変換する関数を返す
        /// </summary>
        static Func<string, List<T>> Cast<T>() => _ => _.Split(' ').Select(Convert<T>()).ToList();

        /// <summary>
        /// 1行の入力をTに応じて変換する関数を返す
        /// </summary>
        static Func<string, T> Convert<T>()
        {
            Type t = typeof(T);
            if (t == typeof(string)) return _ => (T) (object) _;
            if (t == typeof(int)) return _ => (T) (object) int.Parse(_);
            if (t == typeof(long)) return _ => (T) (object) long.Parse(_);
            if (t == typeof(double)) return _ => (T) (object) double.Parse(_);
            if (t == typeof(List<string>)) return _ => (T) (object) Cast<string>()(_);
            if (t == typeof(List<int>)) return _ => (T) (object) Cast<int>()(_);
            if (t == typeof(List<long>)) return _ => (T) (object) Cast<long>()(_);
            if (t == typeof(List<double>)) return _ => (T) (object) Cast<double>()(_);

            throw new NotSupportedException(t + "is not supported.");
        }

        static T Convert<T>(string s) => Convert<T>()(s);

        static string String() => Console.ReadLine();

        static List<string> String(long rowNumber) => new bool[rowNumber].Select(_ => String()).ToList();

        /// <summary>
        /// 1行の値の入力
        /// </summary>
        public static void Cin<T>(out T a) => a = Convert<List<T>>(String())[0];

        public static void Cin<T1, T2>(out T1 a1, out T2 a2)
        {
            var v = Convert<List<string>>(String());
            a1 = Convert<T1>(v[0]);
            a2 = Convert<T2>(v[1]);
        }

        public static void Cin<T1, T2, T3>(out T1 a1, out T2 a2, out T3 a3)
        {
            var v = Convert<List<string>>(String());
            a1 = Convert<T1>(v[0]);
            a2 = Convert<T2>(v[1]);
            a3 = Convert<T3>(v[2]);
        }

        public static void Cin<T1, T2, T3, T4>(out T1 a1, out T2 a2, out T3 a3, out T4 a4)
        {
            var v = Convert<List<string>>(String());
            a1 = Convert<T1>(v[0]);
            a2 = Convert<T2>(v[1]);
            a3 = Convert<T3>(v[2]);
            a4 = Convert<T4>(v[3]);
        }

        public static void Cin<T1, T2, T3, T4, T5>(out T1 a1, out T2 a2, out T3 a3, out T4 a4, out T5 a5)
        {
            var v = Convert<List<string>>(String());
            a1 = Convert<T1>(v[0]);
            a2 = Convert<T2>(v[1]);
            a3 = Convert<T3>(v[2]);
            a4 = Convert<T4>(v[3]);
            a5 = Convert<T5>(v[4]);
        }

        public static void Cin<T1, T2, T3, T4, T5, T6>(out T1 a1, out T2 a2, out T3 a3, out T4 a4, out T5 a5, out T6 a6)
        {
            var v = Convert<List<string>>(String());
            a1 = Convert<T1>(v[0]);
            a2 = Convert<T2>(v[1]);
            a3 = Convert<T3>(v[2]);
            a4 = Convert<T4>(v[3]);
            a5 = Convert<T5>(v[4]);
            a6 = Convert<T6>(v[5]);
        }

        /// <summary>
        /// 複数行の値の入力
        /// </summary>
        public static void Cin<T>(long n, out List<T> l) => l = String(n).Select(Convert<T>()).ToList();

        public static void Cin<T1, T2>(long n, out T1[] l1, out T2[] l2)
        {
            l1 = new T1[n];
            l2 = new T2[n];
            for (int i = 0; i < n; i++)
            {
                var l = String().Split(' ').ToList();
                l1[i] = Convert<T1>(l[0]);
                l2[i] = Convert<T2>(l[1]);
            }
        }

        public static void Cin<T1, T2, T3>(long n, out List<T1> l1, out List<T2> l2, out List<T3> l3)
        {
            l1 = new List<T1>();
            l2 = new List<T2>();
            l3 = new List<T3>();
            foreach (List<string> l in String(n).Select(Convert<List<string>>()))
            {
                l1.Add(Convert<T1>(l[0]));
                l2.Add(Convert<T2>(l[1]));
                l3.Add(Convert<T3>(l[2]));
            }
        }

        public static void Cin<T1, T2, T3, T4>(long n, out List<T1> l1, out List<T2> l2, out List<T3> l3,
            out List<T4> l4)
        {
            l1 = new List<T1>();
            l2 = new List<T2>();
            l3 = new List<T3>();
            l4 = new List<T4>();
            foreach (List<string> l in String(n).Select(Convert<List<string>>()))
            {
                l1.Add(Convert<T1>(l[0]));
                l2.Add(Convert<T2>(l[1]));
                l3.Add(Convert<T3>(l[2]));
                l4.Add(Convert<T4>(l[3]));
            }
        }

        /// <summary>
        /// 1行に書かれた複数の値の入力
        /// </summary>
        public static void Cin<T>(out List<T> lArr) => lArr = Convert<List<T>>(String());

        /// <summary>
        /// h行の行列の入力
        /// </summary>
        public static void Cin<T>(long h, out List<List<T>> map) => map = String(h).Select(Convert<List<T>>()).ToList();
    }

    class Program
    {
        public static void Main(string[] args)
        {
            StreamWriter streamWriter = new StreamWriter(Console.OpenStandardOutput()) {AutoFlush = false};
            Console.SetOut(streamWriter);
            new Solver().Solve();
            Console.Out.Flush();
        }

        public static void Debug()
        {
            new Solver().Solve();
        }
    }

    class Solver
    {
        private int N;
        int[] A;
        int[] B;

        public void Solve()
        {
            Cin(out N);
            Cin(N - 1, out A, out B);

            Dictionary<int, List<int>> neighbor = new Dictionary<int, List<int>>();
            Dictionary<int, List<int>> neighbor2 = new Dictionary<int, List<int>>();
            for (int i = 0; i < N + 1; i++)
            {
                neighbor.Add(i, new List<int>());
                neighbor2.Add(i, new List<int>());
            }

            for (int i = 0; i < N - 1; i++)
            {
                neighbor[A[i]].Add(B[i]);
                neighbor2[A[i]].Add(B[i]);
                neighbor[B[i]].Add(A[i]);
                neighbor2[B[i]].Add(A[i]);
            }


            HashSet<int> memo = new HashSet<int>();
            int[] dist1 = new int[N + 1];
            memo.Add(1);
            Func<int, int, int, int> dfs = null;
            dfs = (v, prev, dist) =>
            {
                dist1[v] = dist;
                foreach (var i in neighbor[v])
                {
                    if (i == prev) continue;
                    dfs(i, v, dist + 1);
                }

                return 0;
            };
            dfs(1, -1, 0);

            int maxIndex = 0;
            for (int i = 1; i <= N; i++)
            {
                if (dist1[i] > dist1[maxIndex]) maxIndex = i;
            }

            // Console.WriteLine(1);

            int[] dist2 = new int[N + 1];

            dfs = (v, prev, dist) =>
            {
                dist2[v] = dist;
                foreach (var i in neighbor[v])
                {
                    if (i == prev) continue;
                    dfs(i, v, dist + 1);
                }

                return 0;
            };
            dfs(maxIndex, -1, 0);
            Console.WriteLine((dist2.Max() + 1) % 3 == 2 ? "Second" : "First");
        }
    }
}