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 Perl (v5.18.2) (judge verdict: Accepted)

#!/usr/bin/perl
use Data::Dumper;
my ($n,$m) = map {$_ - 0} split(/\s+/o,<STDIN>);

my @tr = ();
$#tr = $n-1;
my @par = ();
$#par = $n-1;

for(my $i=0;$i<$n;$i++){
  $par[$i] = $i;
}

for(my $i=0;$i<$m;$i++){
  my ($x,$y,$z) = map {$_ - 0} split(/\s+/o,<STDIN>);
  unite($x-1,$y-1);
}

my %dum = ();
for(my $i=0;$i<$n;$i++){
  $dum{&root($i)} = 1;
}
my @d2 = keys %dum;
my $res = 1 + $#d2;
print "$res\n";

exit(0);

sub root {
  my $x = shift;
  return $x if $par[$x] == $x;
  my $r = &root($par[$x]);
  $par[$x] = $r;
  return $r;
}

sub unite {
  my $x = shift;
  my $y = shift;
  my $rx = &root($x);
  my $ry = &root($y);
  return if( $rx == $ry );
  $par[$rx] = $ry;
}