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 PyPy3 (2.4.0) (judge verdict: Accepted)


from collections import defaultdict


def get_dic(dic_data, x):
    while x != dic_data[x]:
        x = dic_data[x]
    return x

def main():
    num, hinto = map(int, input().split())
    data_flg = [-1 for i in range(num + 1)]
    ans = 0
    modoru = 0

    dic_data = {i: i for i in range(num + 1)}

    real_ans = 0

    for i in range(hinto):
        x, y, z = map(int, input().split())

        if data_flg[x] == -1 and data_flg[y] == -1:
            data_flg[x] = ans
            data_flg[y] = ans
            ans += 1
            real_ans += 1
        elif data_flg[x] == -1 or data_flg[y] == -1:
            aaa = max(data_flg[x], data_flg[y])
            data_flg[x] = aaa
            data_flg[y] = aaa
        else:
            # print(data_flg[x], data_flg[y])
            nnn = get_dic(dic_data, data_flg[x])
            bbb = get_dic(dic_data, data_flg[y])
            if nnn != bbb:
                dic_data[nnn] = ans
                dic_data[bbb] = ans
                modoru += 1
                ans += 1

    real_ans -= modoru

    for i in range(1, num + 1):
        if data_flg[i] == -1:
            real_ans += 1

    print(real_ans)




if __name__ == '__main__':
    main()