Problem:
Score : 500 points

Problem Statement

There are N cards placed face down in a row. On each card, an integer 1 or 2 is written.

Let A_i be the integer written on the i-th card.

Your objective is to guess A_1, A_2, ..., A_N correctly.

You know the following facts:

For each i = 1, 2, ..., M, the value A_{X_i} + A_{Y_i} + Z_i is an even number.

You are a magician and can use the following magic any number of times:

Magic: Choose one card and know the integer A_i written on it. The cost of using this magic is 1.

What is the minimum cost required to determine all of A_1, A_2, ..., A_N?

It is guaranteed that there is no contradiction in given input.

Constraints

All values in input are integers.

2 \leq N \leq 10^5

1 \leq M \leq 10^5

1 \leq X_i < Y_i \leq N

1 \leq Z_i \leq 100

The pairs (X_i, Y_i) are distinct.

There is no contradiction in input. (That is, there exist integers A_1, A_2, ..., A_N that satisfy the conditions.)

Input

Input is given from Standard Input in the following format:

N M
X_1 Y_1 Z_1
X_2 Y_2 Z_2
\vdots
X_M Y_M Z_M

Output

Print the minimum total cost required to determine all of A_1, A_2, ..., A_N.

Sample Input 1

3 1
1 2 1

Sample Output 1

2

You can determine all of A_1, A_2, A_3 by using the magic for the first and third cards.

Sample Input 2

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

Sample Output 2

2

Sample Input 3

100000 1
1 100000 100

Sample Output 3

99999

Solution in C# (Mono 4.6.2.0) (judge verdict: Wrong Answer)

using System;
using System.Collections.Generic;
using System.Linq;

namespace abc126
{
    class ProgramE
    {
        struct Info
        {
            public int X;
            public int Y;
            public bool IsEvenTotal;
        }

        static void Main(string[] args)
        {
            var tmp = Console.ReadLine().Split(' ').Select(_ => int.Parse((string) _)).ToArray();

            // var tmp = new int[] {6, 5};
            var n = tmp[0];
            var m = tmp[1];
            var infos = new List<Info>();

            /*
            infos.Add(new Info() {X = 0, Y = 1, IsEvenTotal = false});
            infos.Add(new Info() {X = 1, Y = 2, IsEvenTotal = true});
            infos.Add(new Info() {X = 0, Y = 2, IsEvenTotal = false});
            infos.Add(new Info() {X = 3, Y = 4, IsEvenTotal = true});
            infos.Add(new Info() {X = 4, Y = 5, IsEvenTotal = false});
            */
            var count = new int[n];

            var hashs = new List<HashSet<int>>();

            for (var im = 0; im < m; im++)
            {
                tmp = Console.ReadLine().Split(' ').Select(_ => int.Parse((string) _)).ToArray();
                var info = new Info()
                {
                    X = tmp[0] - 1,
                    Y = tmp[1] - 1,
                    IsEvenTotal = tmp[2] % 2 == 0
                };
                infos.Add(info);
            }

            foreach (var info in infos)
            {
                count[info.X]++;
                count[info.Y]++;

                HashSet<int> xHash = null;
                HashSet<int> yHash = null;

                foreach (var hash in hashs)
                {
                    if (hash.Contains(info.X))
                    {
                        xHash = hash;
                    }
                    if (hash.Contains(info.Y))
                    {
                        yHash = hash;
                    }
                }

                if (xHash == null && yHash == null)
                {
                    var newHash = new HashSet<int>();
                    newHash.Add(info.X);
                    newHash.Add(info.Y);
                    hashs.Add(newHash);
                    continue;
                }
                if (xHash == yHash)
                {
                    continue;
                }

                if (yHash == null)
                {
                    xHash.Add(info.Y);
                    continue;
                }
                if (xHash == null)
                {
                    yHash.Add(info.X);
                    continue;
                }
                foreach (var i in yHash)
                {
                    xHash.Add(i);
                    hashs.Remove(xHash);
                }
            }

            var numCount1 = 0;
            var numCountOver2 = 0;

            for (var ni = 0; ni < n; ni++)
            {
                if (count[ni] > 1)
                {
                    numCountOver2++;
                }
                else if (count[ni] == 1)
                {
                    numCount1++;
                }
            }

            var numCount0 = n - numCountOver2 - numCount1;
            var result = numCount0 + hashs.Count;

            Console.WriteLine(result);
        }
    }
}