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: Runtime Error)

using System;
using System.Collections.Generic;
using System.Linq;
using BitArray = System.Collections.BitArray;
using BigInteger = System.Numerics.BigInteger;

namespace AtCoderProject
{
    public class Program
    {
        public object Calc()
        {
            var line = consoleReader.SplitInt();
            var N = line[0];
            var M = line[1];
            var cond = consoleReader.RepeatSplitInt(M).Select(l => new Condition { xi = l[0] - 1, yi = l[1] - 1 }).ToArray();
            var groups = new Group[N];

            foreach (var c in cond)
            {
                if (groups[c.xi] == null && groups[c.yi] == null)
                {
                    groups[c.xi] = groups[c.yi] = new Group();
                    groups[c.xi].list = new List<int> { c.xi, c.yi };
                }
                else if (groups[c.xi] != null && groups[c.yi] != null)
                {
                    if (groups[c.xi].list.Count < groups[c.yi].list.Count)
                    {
                        groups[c.yi].list.AddRange(groups[c.xi].list);
                        groups[c.xi].list = groups[c.yi].list;
                    }
                    else
                    {
                        groups[c.xi].list.AddRange(groups[c.yi].list);
                        groups[c.yi].list = groups[c.xi].list;
                    }
                }
                else if (groups[c.xi] != null)
                {
                    groups[c.yi] = groups[c.xi];
                    groups[c.xi].list.Add(c.yi);
                }
                else
                {
                    groups[c.xi] = groups[c.yi];
                    groups[c.xi].list.Add(c.xi);
                }
            }

            var count = 0;
            var setOfList = new HashSet<List<int>>();
            foreach (var g in groups)
            {
                if (g == null)
                    ++count;
                else if (setOfList.Add(g.list))
                    ++count;
            }
            return count;
        }

        struct Condition
        {
            public int xi;
            public int yi;
        }
        public class Group
        {
            public List<int> list;
        }

        public const int mod = 1000000007;
        #region いつもの
        private readonly ConsoleReader consoleReader;
        public Program() : this(new ConsoleReader()) { }
        public Program(ConsoleReader consoleReader) { this.consoleReader = consoleReader; }
        static void Main() => Console.WriteLine(new Program().Calc());
        public static string MultiLine<T>(IEnumerable<T> source) => string.Join("\n", source);
        #endregion
    }

    #region Console
    public class ConsoleReader { public virtual string String() => Console.ReadLine(); public int Int() => int.Parse(String()); public long Long() => long.Parse(String()); public ulong ULong() => ulong.Parse(String()); public double Double() => double.Parse(String()); public string[] Split() => String().Split().ToArray(); public int[] SplitInt() => String().Split().Select(int.Parse).ToArray(); public long[] SplitLong() => String().Split().Select(long.Parse).ToArray(); public ulong[] SplitULong() => String().Split().Select(ulong.Parse).ToArray(); public double[] SplitDouble() => String().Split().Select(double.Parse).ToArray(); public IEnumerable<string> Repeat(int count) { for (int i = 0; i < count; i++) yield return String(); } public IEnumerable<int> RepeatInt(int count) { for (int i = 0; i < count; i++) yield return Int(); } public IEnumerable<long> RepeatLong(int count) { for (int i = 0; i < count; i++) yield return Long(); } public IEnumerable<string[]> RepeatSplit(int count) { for (int i = 0; i < count; i++) yield return Split(); } public IEnumerable<int[]> RepeatSplitInt(int count) { for (int i = 0; i < count; i++) yield return SplitInt(); } }
    #endregion
}