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 static System.Console;
using static System.Math;

namespace AtTest.ABC_126
{
    class E
    {
        static void Main(string[] args)
        {
            Method(args);
        }

        static void Method(string[] args)
        {
            int[] nm = ReadInts();
            int n = nm[0];
            int m = nm[1];
            UnionFind unionFind = new UnionFind(n);
            for(int i = 0; i < m; i++)
            {
                int[] xyz = ReadInts();
                unionFind.Unite(xyz[0] - 1, xyz[1] - 1);
            }

            int cnt = 0;
            for(int i = 0; i < n; i++)
            {
                if (i == unionFind.Root(i)) cnt++;
            }

            WriteLine(cnt);
        }

        class UnionFind
        {
            int[] tree;
            int[] size;

            public UnionFind(int length)
            {
                tree = new int[length];
                size = new int[length];
                for (int i = 0; i < length; i++)
                {
                    tree[i] = i;
                    size[i] = 0;
                }
            }

            public int Root(int x)
            {
                int rx = x;
                while (tree[rx] != rx)
                {
                    rx = tree[rx];
                }
                tree[x] = rx;
                return rx;
            }

            public bool IsSame(int x, int y)
            {
                return Root(x) == Root(y);
            }

            public void Unite(int x, int y)
            {
                int rx = Root(x);
                int ry = Root(y);
                if (rx == ry) return;

                if (rx > ry)
                {
                    int temp = rx;
                    rx = ry;
                    ry = temp;
                }
                tree[ry] = rx;
                size[rx] += size[ry];
            }

            public int GetSize(int x)
            {
                return size[Root(x)];
            }
        }

        private static string Read() { return ReadLine(); }
        private static char[] ReadChars() { return Array.ConvertAll(Read().Split(), a => a[0]); }
        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); }
    }
}