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: Accepted)

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

namespace ABC126
{
    class E
    {
        static void Main()
        {

            int[] input = Console.ReadLine().Split().Select(int.Parse).ToArray();

            int N = input[0];
            int M = input[1];

            List<int>[] list = new List<int>[N];

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

            int x = 0;
            int y = 0;
            for (int i = 0; i < M; i++)
            {
                input = Console.ReadLine().Split().Select(int.Parse).ToArray();
                x = input[0] - 1;
                y = input[1] - 1;
                list[x].Add(y);
                list[y].Add(x);
            }

            int count = 0;
            bool[] Used = new bool[N];

            Queue<int> q = new Queue<int>();
            for (int i = 0; i < N; i++)
            {
                if (Used[i]) continue;
                count++;
                Used[i] = true;
                q.Enqueue(i);

                while (q.Any())
                {
                    foreach (var item in list[q.Dequeue()])
                    {
                        if (Used[item]) continue;
                        Used[item] = true;
                        q.Enqueue(item);
                    }
                }
            }
            Console.WriteLine(count);
        }
    }
}