C++ :

/*
	author :hzoi_ztx
	title  :棋子 
	ALG    :DFS 
	CMT    :二分图思想 嗯,只能说忘了KM怎么写了 = = 
			将未访问过的点加入集合,然后模拟模拟就粗来了
			预计能过一些点吧 
	[2014 10 23]
*/

#include <cstdio>
#include <map>

#define  maxn  200010
#define  maxe  500010
#define  maxt  400010

typedef long long ll ;

struct FST{
	ll to , next ;
} e[maxe] ; ll star[maxt] = {0} , tote = 0 ;

void addEdge(ll u , ll v) {
	tote ++ ; e[tote].to = v ;
	e[tote].next = star[u] ; star[u] = tote ;
}

ll n , ans = 0 ;
ll cntx = 0 , cnty = 200000 ;
std::map<ll,ll>existx ;
std::map<ll,ll>existy ;
bool visit[maxt] = {0} ;

ll Left , Right ;

void dfs(ll s, bool left) {
	ll t , p ;
	if (left) {
		Left ++ ; ans += Right ;
	} else {
		Right ++ ; ans += Left ;
	}
	for (p=star[s],t=e[p].to;p;p=e[p].next,t=e[p].to) {
		if (!visit[t]) {
			visit[t] = true ; dfs(t , !left) ;
		}
	}
}

int main() {
//	#define READ
	#ifdef  READ
		freopen("chess.in" ,"r",stdin ) ;
		freopen("chess.out","w",stdout) ;
	#endif
	ll i , x , y ;
	scanf("%lld", &n ) ;
	existx.clear() ;
	existy.clear() ;
	for (i = 1 ; i <= n ; i ++ ) {
		scanf("%lld%lld", &x , &y ) ;
		if (existx[x]) x = existx[x] ;
		else { existx[x] = ++cntx ; x = cntx ; }
		if (existy[y]) y = existy[y] ;
		else { existy[y] = ++cnty ; y = cnty ; }
		addEdge(x , y) ; addEdge(y , x) ;
	}
	for (i = 1 ; i <= cntx ; i ++ ) {
		if (!visit[i]) {
			visit[i] = true ;
			Left = 0 ; Right = 0 ;
			dfs(i , true) ;
		}
	}
	printf("%lld\n", ans ) ;
	#ifdef  READ
		fclose(stdin ) ;
		fclose(stdout) ;
	#endif
	return 0 ;
}