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 Python (3.4.3) (judge verdict: Accepted)

import sys, math, collections, heapq, itertools
F = sys.stdin
def single_input(): return F.readline().strip("\n")
def line_input(): return F.readline().strip("\n").split()
def gcd(a, b):
    a, b = max(a, b), min(a, b)
    while a % b > 0: a, b = b, a % b
    return b
 
def find(a, L):
    if L[a] == a: return a
    else: 
        L[a] = find(L[a], L)
        return L[a]
 
def unite(a, b, L, R):
    a = find(a, L)
    b = find(b, L)
    if a == b: return
    if R[a] < R[b]:
        L[a] = b
    else:
        L[b] = a
        if R[a] == R[b]: R[a] += 1
    
  
def solve():
    N, M = map(int, line_input())
    parent = [int(i) for i in range(N)]
    edge = [[] for i in range(N)]
    rank = [0] * N
    for i in range(M):
        x, y, z = map(int, line_input())
        unite(x-1, y-1, parent, rank)
    for i in range(N):
        parent[i] = find(i, parent)
    print(len(set(parent)))
    return 0
  
if __name__ == "__main__":
    solve()