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.Linq;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        var numx = ReadInts();
        var n = numx[0];
        var m = numx[1];
        var points = Enumerable.Repeat(1, m).Select(_ => ReadInts()).OrderBy(p => p[0]).ToArray();
        var hashSet = new HashSet<int>();
        var left = n;
        foreach (var item in points)
        {
            if (hashSet.Add(item[0]) | hashSet.Add(item[1]))
                left--;
        }

        Console.WriteLine(left);
    }

    static int Caloc(int v, int w, int n)
    {
        n++;
        var vp = GetParents(v-1, n);
        var wp = GetParents(w-1, n);
        var pp = vp.Zip(wp, (p, q) => new Point(p, q)).TakeWhile(p => p.X == p.Y).Select(p => p.X).ToArray();
        return GetNode(pp, n) + 1;
    }


    static int GetNode(IEnumerable<int> source, int n)
    {
            return source.Aggregate(0, (a, p) => a * n + p);
    }
    static IEnumerable<int> GetParents(int v, int n)
    {
        return GetParentsItr(v, n).Reverse();
    }
    static IEnumerable<int> GetParentsItr(int v, int n)
    {
        while (v > 0)
        {
            yield return v % n;
            v /= n;
        }
    }

    #region Utils
    static int[] ReadInts()
    {
        return Console.ReadLine().Split().Select(int.Parse).ToArray();
    }
    #endregion
}

struct Point
{
    public Point(int x, int y)
    {
        X = x;
        Y = y;
    }

    public int X { get; }
    public int Y { get; }
}