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;
namespace 令和{
    class ABC{
        static void Main(){
            string[] n_m = Console.ReadLine().Split();
            int n = int.Parse(n_m[0]);
            int m = int.Parse(n_m[1]);
            UnionFind uf = new UnionFind(n);
            for(int i=0;i<m;i++){
               string[] x_y_z = Console.ReadLine().Split();
               uf.Unite(int.Parse(x_y_z[0])-1,int.Parse(x_y_z[1])-1);
            }
            bool[] isRoot = new bool[n];
            for(int i=0;i<n;i++){
                isRoot[i] = false;
            }
            int ans = 0;
            for(int i=0;i<n;i++){
                if(isRoot[uf.root(i)]==false){
                    isRoot[uf.root(i)] = true;
                    ans ++;
                }
            }
            Console.WriteLine(ans);
        }
    }

    class UnionFind{
        public UnionFind(int n){
            this.parent = new int[n];
            for(int i=0;i<n;i++){
                parent[i] = i;
            }
        }

        public int[] parent;

        public int root(int x){
            if(parent[x]==x){return x;}
            return root(parent[x]);
        }

        public void Unite(int x, int y){
            int rx = root(x);
            int ry = root(y);
            if(rx==ry){return;}
            parent[ry] = rx;
        }
        public void Merge(int x, int y){Unite(x,y);}

        public bool SameParent(int x, int y){
            if(root(x)==root(y)){return true;}
            return false;
        }
    }
}