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 <bits/stdc++.h>
using namespace std;
#define rep(i, m, n) for(int i=m; i<n; i++)
typedef long long ll;
typedef pair<int, int> P;
typedef pair<ll, ll> Pll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<ll> vll;
template <typename T> bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1;} return 0; }
template <typename T> bool chmin(T &a, const T &b) { if (a>b) { a=b; return 1;} return 0; }

struct UnionFind
{
    vi par;
    vi sizes;
    UnionFind(int n) : par(n), sizes(n,1){
        rep(i,0,n) par[i] = i;
    }
    int find(int x){
        if(par[x]==x) return x;
        return par[x] = find(par[x]);
    }
    void unite(int x, int y){
        x = find(x);
        y = find(y);
        if(x==y) return;
        if(sizes[x]<sizes[y]) swap(x,y);
        par[y] = x;
        sizes[x] += sizes[y];
    }
    bool same(int x, int y){
        return find(x)==find(y);
    }
    int size(int x){
        return sizes[find(x)];
    }
};
int main() {
    int n,m; cin>>n>>m;
    UnionFind uf(n);
    rep(i,0,m){
        int x,y,z; cin>>x>>y>>z;
        x--,y--;
        uf.unite(x,y);
    }
    int ans[n]={0};
    rep(i,0,n){
        ans[uf.find(i)]++;
    }
    int res=0;
    rep(i,0,n) if(ans[i]>0) res++;
    cout<<res<<endl;
}