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