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.Runtime.CompilerServices;
using System.Text;
using System.Threading.Tasks;

namespace ABC126_E
{
    class Program
    {
        static void Main(string[] args)
        {
            var NM = Console.ReadLine().Split().Select(int.Parse).ToArray();
            var N = NM[0];
            var M = NM[1];

            var U = new UnionFind(N);
            for (int i = 0; i < M; i++)
            {
                var XYZ = Console.ReadLine().Split().Select(int.Parse).ToArray();
                var X = XYZ[0];
                var Y = XYZ[1];
                var Z = XYZ[2];

                U.TryUnite(X - 1, Y - 1);
            }

            Console.WriteLine(U.GroupCount);
        }

        class UnionFind
        {
            public int Size { get; private set; }
            public int GroupCount { get; private set; }
            List<int> Sizes;
            List<int> Parent;
            public UnionFind(int count)
            {
                Size = 0;
                GroupCount = 0;
                Parent = new List<int>(count);
                Sizes = new List<int>(count);
                ExtendSize(count);
            }
            public bool TryUnite(int x, int y)
            {
                int xp = Find(x);
                int yp = Find(y);
                if (yp == xp) return false;
                if (Sizes[xp] < Sizes[yp])
                {
                    var tmp = xp;
                    xp = yp;
                    yp = tmp;
                }
                GroupCount--;
                Parent[yp] = xp;
                Sizes[xp] += Sizes[yp];
                return true;
            }
            public IEnumerable<int> AllRepresents => Parent.Where(x => x == Parent[x]);
            public int GetSize(int x) => Sizes[Find(x)];
            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            public int Find(int x)
            {
                while (x != Parent[x])
                {
                    Parent[x] = Parent[Parent[x]];
                    x = Parent[x];
                }
                return x;
            }
            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            public void ExtendSize(int treeSize)
            {
                if (treeSize <= Size) return;
                Parent.Capacity = treeSize;
                Sizes.Capacity = treeSize;
                while (Size < treeSize)
                {
                    Parent.Add(Size);
                    Sizes.Add(1);
                    Size++;
                    GroupCount++;
                }
            }
        }
    }


    }