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

import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.InputMismatchException;
import java.util.LinkedList;
import java.util.Queue;


public class C {
	private static class Pair {
		private int u, v;
		
		public Pair(int a, int b) {
			u=a;
			v=b;
		}
		
		public int hashCode() {
			return u+v+u*v;
		}
		
		public boolean equals(Object o) {
			Pair edge = (Pair) o;
			return u==edge.u && v==edge.v;
		}
	}
	
	private static int n;
	private static int[][] a;

	public static void main(String[] args) {
		n = ini();
		a = new int[n][2];
		
		HashMap<Pair, ArrayList<Integer>> g = new HashMap<>();
		
		for(int i=0; i<n; i++) {
			a[i][0] = ini();
			a[i][1] = ini();
			Pair pair = new Pair(a[i][0], a[i][1]);
			if (!g.containsKey(pair)) {
				g.put(pair, new ArrayList<>());
			}
			g.get(pair).add(i);
		}
		int cc = 0;
		
		
		boolean[] mark = new boolean[n];
		
		for(int i=0; i<n; i++) {
			if (mark[i]) continue;
			
			cc++;
			
			Queue<Integer> queue = new LinkedList<>();
			queue.add(i);
			
			while(!queue.isEmpty()) {
				int u = queue.poll();
				int x = a[u][0];
				int y = a[u][1];
				
				for(int j=1; j<=1000; j++) {
					Pair pair = new Pair(x, j);
					if (g.containsKey(pair)) {
						for(int k: g.get(pair)) {
							if (mark[k]) continue;
							mark[k] = true;
							queue.add(k);
						}
					}
				}
				
				for(int j=1; j<=1000; j++) {
					Pair pair = new Pair(j, y);
					if (g.containsKey(pair)) {
						for(int k: g.get(pair)) {
							if (mark[k]) continue;
							mark[k] = true;
							queue.add(k);
						}
					}
				}
				
			}
			
			
		}

//		println("CC "+cc);
		println(cc-1);
		
		out.flush();
		out.close();

	}

	//NONPROBLEM CODE

	private static InputReader in = new InputReader(System.in);
	private static PrintWriter out = new PrintWriter(System.out);

	private static class InputReader {

		private final InputStream stream;
		private final byte[] buf = new byte[8192];
		private int curChar, snumChars;

		public InputReader(InputStream st) {
			this.stream = st;
		}

		public int read() {
			if (snumChars == -1)
				throw new InputMismatchException();
			if (curChar >= snumChars) {
				curChar = 0;
				try {
					snumChars = stream.read(buf);
				} catch (IOException e) {
					throw new InputMismatchException();
				}
				if (snumChars <= 0)
					return -1;
			}
			return buf[curChar++];
		}

		public int nextInt() {
			int c = read();
			while (isSpaceChar(c)) {
				c = read();
			}
			int sgn = 1;
			if (c == '-') {
				sgn = -1;
				c = read();
			}
			int res = 0;
			do {
				res *= 10;
				res += c - '0';
				c = read();
			} while (!isSpaceChar(c));
			return res * sgn;
		}

		public long nextLong() {
			int c = read();
			while (isSpaceChar(c)) {
				c = read();
			}
			int sgn = 1;
			if (c == '-') {
				sgn = -1;
				c = read();
			}
			long res = 0;
			do {
				res *= 10;
				res += c - '0';
				c = read();
			} while (!isSpaceChar(c));
			return res * sgn;
		}

		public int[] nextIntArray(int n) {
			int a[] = new int[n];
			for (int i = 0; i < n; i++) {
				a[i] = nextInt();
			}
			return a;
		}

		public String readString() {
			int c = read();
			while (isSpaceChar(c)) {
				c = read();
			}
			StringBuilder res = new StringBuilder();
			do {
				res.appendCodePoint(c);
				c = read();
			} while (!isSpaceChar(c));
			return res.toString();
		}

		public String nextLine() {
			int c = read();
			while (isSpaceChar(c))
				c = read();
			StringBuilder res = new StringBuilder();
			do {
				res.appendCodePoint(c);
				c = read();
			} while (!isEndOfLine(c));
			return res.toString();
		}

		public boolean isSpaceChar(int c) {
			return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
		}

		private boolean isEndOfLine(int c) {
			return c == '\n' || c == '\r' || c == -1;
		}

	}

	//INPUT SHORTCUTS

	private static int[] ina(int n) {
		int[] temp = new int[n];
		for (int i = 0; i < n; i++) {
			temp[i] = in.nextInt();
		}
		return temp;
	}

	private static int ini() {
		return in.nextInt();
	}

	//OTHER SHORTCUTS
	public static void sort(int[] a) {
		Arrays.sort(a);
	}

	//PRINT SHORTCUTS

	private static void println(Object... o) {
		for (Object x : o) {
			out.write(x + " ");
		}
		out.write("\n");
		out.flush();
	}

	private static void print(Object... o) {
		for (Object x : o) {
			out.write(x + " ");
		}
		out.flush();
	}

	private static void debug(Object... o) {
		for (Object x : o) {
			out.write(x + " ");
		}
		out.write("\n");
		out.flush();
	}

	private static HashMap<Integer, ArrayList<Integer>> intree(int n) {

		HashMap<Integer, ArrayList<Integer>> g = new HashMap<>();
		for (int i = 0; i < n; i++) {
			g.put(i, new ArrayList<>());
		}

		for (int i = 0; i < n - 1; i++) {
			int u = ini() - 1;
			int v = ini() - 1;
			g.get(u).add(v);
			g.get(v).add(u);
		}

		return g;
	}
}
