#include <cstdio>  	#define COGS
#include <cstring>
using namespace std;
int f[100005] ={0};
int find(int x){
	if(f[x]!=x)f[x]=find(f[x]);
	return f[x];
}

void Init(){
	for(int i=1; i<=100000; i++)f[i]=i;
	int a,b, FAIL=0;
	while(scanf("%d%d", &a, &b)!=EOF&&a!=-1&&b!=-1){
		int fa =find(a), fb =find(b);
		if(fa==fb)FAIL++;
		else f[fb]=fa;
	}
	printf("%d", FAIL);
}
int main(){
	#ifdef COGS
	freopen("explosion.in", "r", stdin);
	freopen("explosion.out", "w", stdout);
	#endif
	Init();
	#ifdef COGS
	fclose(stdin);
	fclose(stdin);
	#endif
	return 0;
}