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: Wrong Answer)

using System ;

namespace Program{
 class Program{
  
  static int []par = new int[100005];
  static void Main(string []args){
   string []buff = Console.ReadLine().Split(' ');
    
   int N = int.Parse(buff[0]); 
   int M = int.Parse(buff[1]);
    
   for(int i = 0 ;i <= N ;i++) par[i] = i ;
    

    
    
   for(int i = 0 ; i < M ;i++){
     buff = Console.ReadLine().Split(' ');
     int X = int.Parse(buff[0]) ;
     int Y = int.Parse(buff[1]) ;
        
     unite(X,Y);

   }
    
   int []c = new int[N];
    
   for(int i =0  ;i < N ;i++){
     c[i] = par[i + 1];
   }
    
   Array.Sort(c);
   int x = c[0];

   int count = 1 ;
    
   for(int i = 1 ; i < N ;i++){

     if( x != c[i]){
       count++;
       x = c[i];
     }
   }
    
   Console.WriteLine(count) ;
  }
   
  static int root( int x){
     if( par[x] == x) return x ;
     return root(par[x]) ;
  }
   
  static void unite( int x ,int y){
    int rootX = root(x);
    int rootY = root(y);
    if( rootX == rootY )return ;
    par[rootY] = rootX ;
  }
 }
}