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.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;
using System.Collections;
static class Extensions
{
    public static int ToInt(this string s) => int.Parse(s);
    public static long ToLong(this string s) => long.Parse(s);
    public static char ToChar(this string s) => char.Parse(s);
    public static double ToDouble(this string s) => double.Parse(s);
    public static int[] ToIntArray(this string s) => s.Replace(',', ' ').Split(' ').Select(x => x.ToInt()).ToArray();
    public static long[] ToLongArray(this string s) => s.Replace(',', ' ').Split(' ').Select(x => x.ToLong()).ToArray();
    public static double[] ToDoubleArray(this string s) => s.Replace(',', ' ').Split(' ').Select(x => x.ToDouble()).ToArray();
    public static Queue<T> ToQueue<T>(this IEnumerable<T> seq) => new Queue<T>(seq);
    public static Stack<T> ToStack<T>(this IEnumerable<T> seq) => new Stack<T>(seq);
    public static HashSet<T> ToHashSet<T>(this IEnumerable<T> seq) => new HashSet<T>(seq);
}
static class MyMath
{
    static private long gcdInner(long a, long b) => (a % b == 0) ? b : gcdInner(b, a % b);
    static public long GCD(long a, long b) => (a > b) ? gcdInner(a, b) : gcdInner(b, a);
    static public long LCM(long a, long b) => (a > b) ? (a / GCD(a, b) * b) : (b / GCD(a, b) * a);
}

class Program
{
    static string[] ReadLines(int n) => Enumerable.Range(0, n).Select(s => Console.ReadLine()).ToArray();
    
    static void Main()
    {
        var nm = Console.ReadLine().ToIntArray();
        int N = nm[0];
        int M = nm[1];
        
        var infoList = Enumerable.Range(0, M).Select(n => Console.ReadLine().ToIntArray())
            .Select(arr => new { X = arr[0] - 1, Y = arr[1] - 1, Z = arr[2] })
            .OrderBy(itm => Math.Min(itm.X, itm.Y))
            .ToList();
        
        //地点iから行ける箇所を取れるようにしておく。
        var ways = Enumerable.Range(0, N).Select(n => new List<int>()).ToArray();
        foreach(var info in infoList)
        {
            ways[info.X].Add(info.Y);
            ways[info.Y].Add(info.X);
        }

        int ans = 0;
        HashSet<int> already = new HashSet<int>();
        for(int i = 0; i < N; i++)
        {
            if (already.Contains(i)) continue;

            Queue<int> q = new Queue<int>();
            q.Enqueue(i);

            while(q.Any())
            {
                var val = q.Dequeue();
                already.Add(val);
                foreach(var next in ways[val])
                {
                    if (already.Contains(next)) continue;

                    q.Enqueue(next);
                }
            }

            ans += 1;
        }

        Console.WriteLine(ans);
        
    }
}