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;
using System.Collections.Generic;

namespace ABC126
{
    public class UnionFind
    {
        int[] par;
        int[] size;

        public UnionFind(int N)
        {
            par = new int[N];
            size = new int[N];
            for (int i = 0; i < N; i++)
            {
                par[i] = i;
                size[i] = 1;
            }
        }

        public int Root(int x)
        {
            if (par[x] == x) return x;
            return par[x] = Root(par[x]);
        }

        public void Unite(int x, int y)
        {
            int rootX = Root(x);
            int rootY = Root(y);
            if (rootX == rootY) return;
            par[rootX] = rootY;
            size[rootY] += size[rootX];
        }

        public bool Same(int x, int y)
        {
            int rootX = Root(x);
            int rootY = Root(y);
            return rootX == rootY;
        }

        public int Size(int x)
        {
            return size[Root(x)];
        }
    }
    
    class Program
    {
        static void Main(string[] args)
        {
            string[] s = Console.ReadLine().Split(' ');
            int N = int.Parse(s[0]);
            int M = int.Parse(s[1]);
            int[] X = new int[M];
            int[] Y = new int[M];
            int[] Z = new int[M];
            Dictionary<int, int> D = new Dictionary<int, int>();
            UnionFind U = new UnionFind(N);
            for (int i = 0; i < M; i++)
            {
                s = Console.ReadLine().Split();
                X[i] = int.Parse(s[0]);
                Y[i] = int.Parse(s[1]);
                Z[i] = int.Parse(s[2]);
                U.Unite(X[i] - 1, Y[i] - 1);
            }
            int res = 0;
            for (int i = 0; i < N; i++)
            {
                if (!D.Keys.Contains(U.Root(i)))
                {
                    D[U.Root(i)] = 1;
                    res++;
                }
            }
            Console.WriteLine(res);
        }
    }
}