//由题意可知，这道题就是图中寻找有几个环
//这题想过的话，其实下面两行代码足以
//#include<stdio.h>
//main(){puts("6");}
//运用类似并查集的思想
#include<stdio.h>
using namespace std;

int* root;
int find(int i){
	if(i != root[i]) root[i] = find(root[i]);
	return root[i];
}

int main(){
    int n, a, b, count = 0;
    scanf("%d", &n);
    root = new int[n + 1];
    for(int i = 1; i <= n; i++) root[i] = 0;
    for(int i = 1; i <= n; i++){
      scanf("%d%d", &a, &b);
		  if(root[a] == 0 && root[b] == 0) root[a] = a, root[b] = a;
		  else if(root[a] == 0 && root[b] != 0) root[a] = find(b);
		  else if(root[a] != 0 && root[b] == 0) root[b] = find(root[a]);
		  else root[find(a)] = root[find(b)];
    }
    for(int i=1; i <= n; i++)
		  if(i == root[i]) count++;

	  printf("%d\n", count);

    return 0;
}

//presented by 大吉大利，今晚AC