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++14 (GCC 5.4.1) (judge verdict: Accepted)

#include <iostream>
#include <string>
#include <vector>
#include <list>
#include <map>
#include <queue>
#include <stack>
#include <algorithm>
#include <fstream>
#include <sstream>
#include <iomanip>

using namespace std;

long long MOD = 1000000007;

vector<int> rank_(0);
vector<int> parent(0);

void DisjointSet(int size){
    for(int i=0; i<size; i++){
        rank_.push_back(0);
        parent.push_back(i);
    }
}

void makeSet(int x){
    parent[x]=x;
    rank_[x]=0;
}

int findSet(int x){
    if (x!=parent[x]){
        parent[x]=findSet(parent[x]);
    }
    return parent[x];
}

bool same(int x, int y){
    return (findSet(x) == findSet(y));
}

void link(int x, int y){
    if (rank_[x] > rank_[y]){
        parent[y]=x;
    }else{
        parent[x]=y;
        if (rank_[x]==rank_[y]){
            rank_[y]+=1;
        }
    }
}

void unite(int x, int y){
    link(findSet(x), findSet(y));
}

int main(){
    int N,M;
    cin >> N >> M;
    vector<int> vec(N,0);
    int ans=N;
    DisjointSet(N);

    for(int i=0; i<M; i++){
        int x,y,z;
        cin >> x >> y >> z;
        x--;y--;
        if(same(x,y))continue;
        ans--;
        unite(x,y);
    }
    cout << ans << endl;
    cin >> N;
}