Bajtek is learning to skate on ice. He's a beginner, so his only mode of transportation is pushing off from a snow drift to the north, east, south or west and sliding until he lands in another snow drift. He has noticed that in this way it's impossible to get from some snow drifts to some other by any sequence of moves. He now wants to heap up some additional snow drifts, so that he can get from any snow drift to any other one. He asked you to find the minimal number of snow drifts that need to be created.

We assume that Bajtek can only heap up snow drifts at integer coordinates.

Input

The first line of input contains a single integer n (1 ≤ n ≤ 100) — the number of snow drifts. Each of the following n lines contains two integers xi and yi (1 ≤ xi, yi ≤ 1000) — the coordinates of the i-th snow drift.

Note that the north direction coinсides with the direction of Oy axis, so the east direction coinсides with the direction of the Ox axis. All snow drift's locations are distinct.

Output

Output the minimal number of snow drifts that need to be created in order for Bajtek to be able to reach any snow drift from any other one.

Examples

Input

2
2 1
1 2


Output

1


Input

2
2 1
4 1


Output

0
/*
 * Remember a 7.0 student can know more than a 10.0 student.
 * Grades don't determine intelligence, they test obedience. 
 * I Never Give Up.
 */
import java.util.*;
import java.util.Map.Entry;
import java.io.*;

import static java.lang.System.out;
import static java.util.Arrays.*;
import static java.lang.Math.*;
public class ContestMain {
	private static Reader in=new Reader();
	private static StringBuilder ans=new StringBuilder();
	private static long MOD=1000000007;//10^9+7 
	private static final int N=1000000;//10^6
	private static final int LIM=26;
//	private static final double PI=3.1415;
	private static ArrayList<Integer> v[]=new ArrayList[N];
//	private static int color[]=new int[N]; //For Graph Coloring
	private static boolean mark[]=new boolean[N];
//	private static BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
	private static void dfs(int node,ArrayList<Integer> r){
		mark[node]=true;
		for(int x:v[node]){
			if(!mark[x]){
				dfs(x,r);
			}
		}
		r.add(node);
	}
	public static void solve(int node,int n,Pair point[]){
		mark[node]=true;
		for(int i=0;i<n;i++){
			if(!mark[i]){
				if(point[i].l==point[node].l||point[i].r==point[node].r){
					solve(i,n,point);
				}
			}
		}
	}
	private static long powmod(long x,long n,long m){
		if(n==0)return 1;
		else if(n%2==0)return(powmod((x*x)%m,n/2,m));
		else return (x*(powmod((x*x)%m,(n-1)/2,m)))%m;
	}
//	private static void shuffle(String[] arr) {
//		for (int i = arr.length - 1; i >= 2; i--) {
//			int x = new Random().nextInt(i - 1);
//	        String temp = arr[x];
//	        arr[x] = arr[i];
//	        arr[i] = temp;
//	    }
//	 }
	public static void main(String[] args) throws IOException{
		int n=in.nextInt();
		Pair point[]=new Pair[n];
		for(int i=0;i<n;i++){
			point[i]=new Pair();
			point[i].l=in.nextInt();
			point[i].r=in.nextInt();
		}
		int cnt=0;
		for(int i=0;i<n;i++){
			if(!mark[i]){
				cnt++;
				solve(i,n,point);
			}
		}
		out.println(cnt-1);
	}
	static class Pair<T> implements Comparable<Pair>{
		int l;
		int r;
		Pair(){
			l=0;
			r=0;
		}
		Pair(int k,int v){
			l=k;
			r=v;
		}
		@Override
		public int compareTo(Pair o) {
			if(l!=o.l)return (int) (l-o.l);
			else return (int) (r-o.r);
		}
		
	}
	static class Reader{
        BufferedReader br;
        StringTokenizer st;
        public Reader()
        {
            br = new BufferedReader(new
                     InputStreamReader(System.in));
        }
 
        String next()
        {
            while (st == null || !st.hasMoreElements())
            {
                try
                {
                    st = new StringTokenizer(br.readLine());
                }
                catch (IOException  e)
                {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }
 
        int nextInt()
        {
            return Integer.parseInt(next());
        }
 
        long nextLong()
        {
            return Long.parseLong(next());
        }
 
        double nextDouble()
        {
            return Double.parseDouble(next());
        }
 
        String nextLine()
        {
            String str = "";
            try
            {
                str = br.readLine();
            }
            catch (IOException e)
            {
                e.printStackTrace();
            }
            return str;
        }
    }
}         