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.Diagnostics;

namespace AtCoder
{
    class Program
    {
        private static string Read() { return Console.ReadLine(); }
        private static int ReadInt() { return int.Parse(Read()); }
        private static long ReadLong() { return long.Parse(Read()); }
        private static double ReadDouble() { return double.Parse(Read()); }
        private static int[] ReadInts() { return Array.ConvertAll(Read().Split(), int.Parse); }
        private static long[] ReadLongs() { return Array.ConvertAll(Read().Split(), long.Parse); }
        private static double[] ReadDoubles() { return Array.ConvertAll(Read().Split(), double.Parse); }
        class Node<T>
        {
            private int m_height;
            private Node<T> m_parent;
            public T Item { get; private set; }
            public Node(T item)
            {
                m_height = 0;
                m_parent = this;
                Item = item;
            }
            public Node<T> Find()
            {
                if (m_parent == this) { return this; }

                Node<T> parent = m_parent.Find();
                m_parent = parent;
                return parent;
            }
            public static void Unite(Node<T> a, Node<T> b)
            {
                Node<T> p = a.Find();
                Node<T> q = b.Find();
                if (p.m_height < q.m_height)
                {
                    p.m_parent = q;
                    q.m_height = Math.Max(p.m_height + 1, q.m_height);
                }
                else
                {
                    q.m_parent = p;
                    p.m_height = Math.Max(q.m_height + 1, p.m_height);
                }
            }
        }

        static int Solve(int N, int M, int[][] infos)
        {
            var nodes = new Node<int>[N];
            for (int i = 0; i < N; ++i) { nodes[i] = new Node<int>(i); }
            foreach (int[] info in infos)
            {
                int x = info[0] - 1;
                int y = info[1] - 1;
                Node<int>.Unite(nodes[x], nodes[y]);
            }
            var set = new HashSet<int>();
            foreach (var node in nodes) { set.Add(node.Find().Item); }
            return set.Count;
        }

        static void Main(string[] args)
        {
            int[] V = ReadInts();
            int N = V[0], M = V[1];
            var infos = new int[M][];
            for (int i = 0; i < M; ++i) { infos[i] = ReadInts(); }
            Console.WriteLine(Solve(N, M, infos));
        }
    }
}