Problem:
Score : 400 points

Problem Statement

There are N persons called Person 1 through Person N.

You are given M facts that "Person A_i and Person B_i are friends." The same fact may be given multiple times.

If X and Y are friends, and Y and Z are friends, then X and Z are also friends. There is no friendship that cannot be derived from the M given facts.

Takahashi the evil wants to divide the N persons into some number of groups so that every person has no friend in his/her group.

At least how many groups does he need to make?

Constraints

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

0 \leq M \leq 2\times 10^5

1\leq A_i,B_i\leq N

A_i \neq B_i

Input

Input is given from Standard Input in the following format:

N M
A_1 B_1
\vdots
A_M B_M

Output

Print the answer.

Sample Input 1

5 3
1 2
3 4
5 1

Sample Output 1

3

Dividing them into three groups such as \{1,3\}, \{2,4\}, and \{5\} achieves the goal.

Sample Input 2

4 10
1 2
2 1
1 2
2 1
1 2
1 3
1 4
2 3
2 4
3 4

Sample Output 2

4

Sample Input 3

10 4
3 1
4 1
5 9
2 6

Sample Output 3

3

Solution in C# (.NET Core 3.1.201) (judge verdict: Accepted)

using System;
using System.Collections.Generic;
using System.Collections;
using System.Linq;
namespace Atcoder_0404
{
    class Program
    {
        static void Main(string[] args)
        {
            var NM = GetInput_int();
            var humanNum = NM[0];
            var infoNum = NM[1];

            var uf =new UnionFind(humanNum+1);

            for(int i = 0; i < infoNum;i++)
            {
                var info = GetInput_int();
                uf.Unite(info[0], info[1]);
            }
            int[] counts = new int[humanNum+1];//代表を務める個数
            for(int i = 0; i <= humanNum; i++)
            {
                counts[ uf.Root(i)]++;
            }

            int max = 0;
            for (int i = 0; i <= humanNum; i++)
            {
                if (max < counts[i]) max = counts[i];
            }
            var result = max ;
            Console.WriteLine(result);
        }


        public class UnionFind
        {
            int[] _parent;

            public UnionFind(int _edgeCount)
            {
                _parent = new int[_edgeCount];
                for (int i = 0; i < _parent.Length; i++)
                {
                    _parent[i] = i;
                }
            }

            public int Root(int x)
            {
                if (_parent[x] == x)
                {
                    return x;
                }
                else
                {
                    _parent[x] = Root(_parent[x]);
                    return _parent[x];
                }
            }

            public bool IsSameRoot(int x, int y)
            {
                return Root(x) == Root(y);
            }

            public void Unite(int x, int y)
            {
                var _xRoot = Root(x);
                var _yRoot = Root(y);
                if (_xRoot == _yRoot) return;
                _parent[_xRoot] = _yRoot;
            }
        }
        #region input


        static string[] GetInput_string()
        {
            var input = Console.ReadLine().Split(' ');
            return input;
        }

        static int[] GetInput_int()
        {
            var input = GetInput_string();
            var result = new int[input.Length];
            for (int i = 0; i < result.Length; i++)
            {
                result[i] = int.Parse(input[i]);
            }
            return result;
        }
        static long[] GetInput_long()
        {
            var input = GetInput_string();
            var result = new long[input.Length];
            for (int i = 0; i < result.Length; i++)
            {
                result[i] = long.Parse(input[i]);
            }
            return result;
        }
        #endregion
        #region sonota
        static void Swap_array<T>(T[] target, int a, int b)
        {
            T temp = target[a];
            target[a] = target[b];
            target[b] = temp;
        }
        static void Swap_list<T>(List<T> target, int a, int b)
        {
            T temp = target[a];
            target[a] = target[b];
            target[b] = temp;
        }
        /// <summary>
        /// 最大公約数
        /// </summary>
        public static int GCD(int a, int b)
        {

            /* 自然数 a > b を確認・入替 */
            if (a < b)
            {
                int tmp = a;
                a = b;
                b = tmp;
            }

            /* ユークリッドの互除法 */
            int r = a % b;
            while (r != 0)
            {
                a = b;
                b = r;
                r = a % b;
            }
            return b;
        }

        /// <summary>
        /// 最小公倍数
        /// </summary>
        public static int LCM(int a, int b)
        {
            int x = a * b;
            b = GCD(a, b);
            return x / b;

        }
        #endregion
        
    }
}