#include<cstdio>
#include<cstring>
#include<cmath>
#include<queue>
#define ma 100001
using namespace std;
int root[ma]={0};
inline int F(int x){
	if(root[x]==x) return x;
	return root[x]=F(root[x]);
}
int main(){
	freopen("explosion.in","r",stdin);
	freopen("explosion.out","w",stdout);
	for(int i=1;i<=ma;i++) root[i]=i;
	int x,y,s=0;
	while(scanf("%d %d",&x,&y)==2){
		int rx=F(x),ry=F(y);
		if(rx==ry) s++;
		else root[ry]=rx;
	}
	printf("%d",s);
	return 0;
}