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)

// デバッグ実行：Ctrl+F5

using System;
using System.Collections.Generic;

class Program
{
    static void Main(string[] args)
    {
        String line;
        line = Console.ReadLine();
        String[] words = line.Split(' ');
        int N = int.Parse(words[0]);
        int M = int.Parse(words[1]);
        Dictionary<int, List<int>> dict = new Dictionary<int, List<int>>();

        int X, Y;
        int count = 0;
        for(int i = 0; i < M; i++)
        {
            line = Console.ReadLine();
            words = line.Split(' ');
            X = int.Parse(words[0]) - 1;
            Y = int.Parse(words[1]) - 1;
            if (!dict.ContainsKey(X))
            {
                dict.Add(X, new List<int>());
            }
            dict[X].Add(Y);
        }
        
        //ルートが何個できるか、検証する
        //できたルートの数だけ、足す
        bool[] found_card = new bool[N];
        for (int i = 0; i < N; i++) found_card[i] = false;
        int route_count = 0;
        List<int> list = new List<int>(dict.Keys);
        for(int i = 0; i < list.Count;)
        {
            route_count++;
            found_card[list[i]] = true;
            foreach (int value in dict[list[i]])
            {
                found_card[value] = true;
            }
            dict.Remove(list[i]);
            list.RemoveAt(i);
            for (int j = 0; j < list.Count; j++)
            {
                if (found_card[list[j]])
                {
                    foreach (int value in dict[list[j]])
                    {
                        found_card[value] = true;
                    }
                    dict.Remove(list[j]);
                    list.RemoveAt(j);
                    j = -1;
                }
                else
                {
                    bool flag = false;
                    foreach(int k in dict[list[j]])
                    {
                        //各要素がどれもないならセーフ
                        if(found_card[k])
                        {
                            flag = true;
                            break;
                        }
                    }
                    //どれかがあった
                    if (flag)
                    {
                        foreach (int value in dict[list[j]])
                        {
                            found_card[value] = true;
                        }
                        dict.Remove(list[j]);
                        list.RemoveAt(j);
                        j = -1;
                    }
                }
            }
        }


        count += route_count;
        for (int i = 0; i < N; i++)
        {
            if (!found_card[i])
            {
                count++;
            }
        }
        Console.WriteLine(count);
    }
    
}