#include<bits/stdc++.h>
#define int long long
#define endl '\n'
#define debug puts("#CheZiHe929")
#define Yes puts("Yes")
#define No puts("No")
const int MAXN=1e6+5;

inline int read(){int x=0,f=1;char ch=getchar();while(ch<'0'||ch>'9'){if (ch=='-') f=-1;ch=getchar();}while(ch>='0'&&ch<='9'){x=x*10+ch-48;ch=getchar();}return x*f;}
inline void print(int x){char st[105];int top=0;if(x==0)putchar('0');if(x<0)putchar('-');while(x){if(x>0)st[++top]=x%10+48;else st[++top]=-(x%10)+48;x/=10;}while(top)putchar(st[top--]);}
inline void println(int x){print(x);putchar('\n');}
inline void printsp(int x){print(x);putchar(' ');}
inline void put(int x,int i,int n){i==n?println(x):printsp(x);}

int n,a[MAXN],b[MAXN];
int ans[MAXN],anss,fa[MAXN];
int find(int x){return x==fa[x]?x:fa[x]=find(fa[x]);}

void merge(int x,int y){
	int fx=find(x),fy=find(y);
	if(fx!=fy)fa[fx]=fy;
}

std::map<int,std::vector<int> > v;

signed main(){
//	freopen(".in","r",stdin);
//	freopen(".out","w",stdout);

	n=read();
	for(int i=1;i<=n;i++){
		a[i]=read(),b[i]=read();
		fa[i]=i;
		v[a[i]].push_back(i);
		if(a[i]!=b[i])
			v[b[i]].push_back(i);
	}

	for(auto p:v){
		std::vector<int> x=p.second;
		for(int i=1;i<x.size();i++)merge(x[0],x[i]);
	}
	
	for(int i=1;i<=n;i++)ans[find(i)]++;
	for(int i=1;i<=n;i++)anss+=ans[i]/2;
	put(anss,1,1);

	return 0;
}