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: Time Limit Exceeded)

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;

namespace ABC126D
{
    class Program
    {
        static void Main(string[] args)
        {
            if (args.Length > 0)
            {
                Console.SetIn(new StreamReader(args[0]));
            }

            new Program().Solve();
        }

        void Solve()
        {
            var temp = Console.ReadLine().Split(' ').Select(int.Parse).ToArray();
            var N = temp[0];
            var M = temp[1];
            var uf = new int[N];

            for (int i = 0; i < N; i++)
            {
                uf[i] = i;
            }

            for (int i = 0; i < M; i++)
            {
                temp = Console.ReadLine().Split(' ').Select(int.Parse).ToArray();
                var X = temp[0] - 1;
                var Y = temp[1] - 1;
                var root = Y;

                while (root != uf[root])
                {
                    // Console.Error.WriteLine("go root: " + root);
                    var temp2 = root;
                    root = uf[root];
                    uf[temp2] = uf[X];
                }

                // Console.Error.WriteLine("reach root: " + root);
                uf[root] = uf[X];
            }

            var roots = new HashSet<int>();

            for (int i = 0; i < N; i++)
            {
                var root = i;

                while (root != uf[root])
                {
                    root = uf[root];
                }

                roots.Add(root);
                // Console.Error.WriteLine("Add: " + root);
            }

            Console.WriteLine(roots.Count);
        }
    }
}