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;

public class Program
{
    private int N, M;
    private int[] X, Y, Z;

    public void Solve()
    {
        var sc = new Scanner();
        N = sc.NextInt();
        M = sc.NextInt();
        X = new int[M];
        Y = new int[M];
        Z = new int[M];
        for (int i = 0; i < M; i++)
        {
            X[i] = sc.NextInt() - 1;
            Y[i] = sc.NextInt() - 1;
            Z[i] = sc.NextInt() % 2;
        }

        var uf = new UnionFind(N);
        int cnt = 0;
        for (int i = 0; i < M; i++)
        {
            if (!uf.Same(X[i], Y[i]))
            {
                uf.Union(X[i],Y[i]);
                cnt++;
            }
        }
        
        Console.WriteLine(N-cnt);
    }

    public static void Main(string[] args)
    {
        new Program().Solve();
    }
}

class UnionFind
{
    private int[] Par, Rank;

    public UnionFind(int max)
    {
        Par = new int[max];
        Rank = new int[max];
        for (int i = 0; i < max; i++)
        {
            Par[i] = i;
        }
    }

    private int Find(int n)
    {
        if (Par[n] == n)
        {
            return n;
        }
        else
        {
            return Find(Par[n]);
        }
    }

    public bool Same(int a, int b)
    {
        return Find(a) == Find(b);
    }

    public void Union(int a, int b)
    {
        a = Find(a);
        b = Find(b);
        if (a == b) return;
        if (Rank[a] < Rank[b])
        {
            Par[a] = b;
        }
        else
        {
            Par[b] = a;
            if (Rank[a] == Rank[b]) Rank[a]++;
        }
    }
}

class Scanner
{
    public Scanner()
    {
        _pos = 0;
        _line = new string[0];
    }

    const char Separator = ' ';
    private int _pos;
    private string[] _line;

    #region スペース区切りで取得

    public string Next()
    {
        if (_pos >= _line.Length)
        {
            _line = Console.ReadLine().Split(Separator);
            _pos = 0;
        }

        return _line[_pos++];
    }

    public int NextInt()
    {
        return int.Parse(Next());
    }

    public long NextLong()
    {
        return long.Parse(Next());
    }

    public double NextDouble()
    {
        return double.Parse(Next());
    }

    #endregion

    #region 型変換

    private int[] ToIntArray(string[] array)
    {
        var result = new int[array.Length];
        for (int i = 0; i < array.Length; i++)
        {
            result[i] = int.Parse(array[i]);
        }

        return result;
    }

    private long[] ToLongArray(string[] array)
    {
        var result = new long[array.Length];
        for (int i = 0; i < array.Length; i++)
        {
            result[i] = long.Parse(array[i]);
        }

        return result;
    }

    private double[] ToDoubleArray(string[] array)
    {
        var result = new double[array.Length];
        for (int i = 0; i < array.Length; i++)
        {
            result[i] = double.Parse(array[i]);
        }

        return result;
    }

    #endregion

    #region 配列取得

    public string[] Array()
    {
        if (_pos >= _line.Length)
            _line = Console.ReadLine().Split(Separator);

        _pos = _line.Length;
        return _line;
    }

    public int[] IntArray()
    {
        return ToIntArray(Array());
    }

    public long[] LongArray()
    {
        return ToLongArray(Array());
    }

    public double[] DoubleArray()
    {
        return ToDoubleArray(Array());
    }

    #endregion
}