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.Linq;
using System.Collections.Generic;

namespace AtCoder_Beginner_Contest_126
{
    class Program
    {
        struct tdst
        {
            public int top;
            public int dst;            
            public tdst(int top, int dst) { this.top = top; this.dst = dst; }
        }
        static void Main(string[] args)
        {
            var NM = Console.ReadLine().Split().Select(int.Parse).ToArray();
            var N = NM[0];//カード数
            var M = NM[1];//式の数
            var node = new List<tdst>[N + 1];
            for(int i=0;i<=N;++i)
            { node[i] = new List<tdst>(); }
            for (int i = 0; i < M; ++i)
            {
                var XYZ = Console.ReadLine().Split().Select(int.Parse).ToArray();
                node[XYZ[0]].Add(new tdst(XYZ[1], 0));
                node[XYZ[1]].Add(new tdst(XYZ[0], 0));
            }
            var chk = new int[N + 1];

            int cnt = 0;
            for (int i = 1; i <= N; ++i)
            {
                if (0 == chk[i])
                {
                    recv(i, node, chk);
                    ++cnt;
                }
            }
            Console.WriteLine(cnt);
        }
        static void recv(int next, List<tdst>[] node, int[] chk)
        {
            foreach (var nd in node[next])
            {
                if (0 != chk[nd.top]) continue;
                chk[nd.top] = 1;
                recv(nd.top, node, chk);
            }
        }
    }
}