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 (GCC 5.4.1) (judge verdict: Accepted)

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <math.h>
#include <stdbool.h>
#define LL long long
#define INF 1<<31-1
#define MIN(x,y) ((x)<(y)?(x):(y))
#define MAX(x,y) ((x)<(y)?(y):(x))
#define FOR(i,a,n) for(i=a;i<n;i++)
#define MOD 1000000007
#define NUM 100001

void swap(int* a,int* b){int tmp=*a;*a=*b;*b=tmp;}
int GCD(int a,int b){int c=1,tmp=MAX(a,b);b=MIN(a,b);a=tmp;while(c!=0){c=a%b;a=b;b=c;}return a;}
int LCM(int a,int b){return a*b/GCD(a,b);}
int POW(LL a,LL n){LL ans=1;while(n>0){if(n&1)ans=ans*a%MOD;a=a*a%MOD;n>>=1;}return (int)ans;}
int icmp(const void* a,const void* b){return *(int*)a-*(int*)b;}
int ccmp(const void* a,const void* b){return *(char*)a-*(char*)b;}
int scmp(const void* a,const void* b){return strcmp(*(char**)a,*(char**)b);}
LL fac[NUM],finv[NUM],inv[NUM];
void comi(){int i;fac[0]=fac[1]=1;finv[0]=finv[1]=1;inv[1]=1;FOR(i,2,NUM){fac[i]=fac[i-1]*i%MOD;inv[i]=MOD-inv[MOD%i]*(MOD/i)%MOD;finv[i]=finv[i-1]*inv[i]%MOD;}}
int com(int n,int k){if(n<k||n<0||k<0)return 0;return fac[n]*(finv[k]*finv[n-k]%MOD)%MOD;}

typedef struct{int s,e,c;}Edge;
int par[NUM];
int UF(){for(int i=0;i<NUM;i++)par[i]=-1;}
int Root(int x){if(par[x]<0)return x;else return par[x]=Root(par[x]);}
int Size(int x){return -par[Root(x)];}
bool Same(int x,int y){return Root(x)==Root(y);}
void Unite(int x,int y){x=Root(x);y=Root(y);if(x!=y){if(Size(x)<Size(y))swap(&x,&y);par[x]+=par[y];par[y]=x;}}


int main(){
	UF();
  int N,M,i,ans=0;
  scanf("%d%d",&N,&M);
	int X[M],Y[M],Z[M],flag[N];
	FOR(i,0,M)scanf("%d%d%d",&X[i],&Y[i],&Z[i]);
	FOR(i,0,M){
		X[i]--;Y[i]--;
		Unite(X[i],Y[i]);
	}
	FOR(i,0,N)flag[i]=0;
	FOR(i,0,N)if(flag[Root(i)]==0){
		flag[Root(i)]=1;
		ans++;
	}
	
  printf("%d\n",ans);
	return 0;
}