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.*;
import java.util.*;

public class Main {
    int parent[ ];
    int find( int x ) {
        if ( x != parent[ x ] ) {
            parent[ x ] = find( parent[ x ] );
        }
        return parent[ x ];
    }
    public void solve( ) throws Throwable {
        int n = in.nextInt( ), x[ ] = new int[ n ], y[ ] = new int[ n ];
        parent = new int[ n ];
        for ( int i = 0; i < n; ++i ) {
            x[ i ] = in.nextInt( );
            y[ i ] = in.nextInt( );
            parent[ i ] = i;
        }
        for ( int i = 0; i < n; ++i ) {
            for ( int j = 0; j < i; ++j ) {
                if ( x[ i ] == x[ j ] || y[ i ] == y[ j ] ) {
                    int u = find( i ), v = find( j );
                    parent[ u ] = parent[ v ];
                }
            }
        }
        int ans =0;
        for ( int i = 0; i < parent.length; ++i ) {
            if( i == parent[ i ] ) {
                ++ans;
            }
        }
        out.println( ans - 1 );

    }

    public void run( ) {
        in = new FastScanner( System.in );
        out = new PrintWriter( new PrintStream( System.out ), true );

        try {
            solve( );
            out.close( );
            System.exit( 0 );
        } catch( Throwable e ) {
            e.printStackTrace( );
            System.exit( -1 ); 
        }
    }


    public void debug( Object...os ) {
        System.err.println( Arrays.deepToString( os ) );
    }

    public static void main( String[ ] args ) {
        ( new Main( ) ).run( );
    }



    private FastScanner in;
    private PrintWriter out;

    private static class FastScanner {
        private int charsRead;
        private int currentRead;
        private byte buffer[ ] = new byte[ 0x1000 ];
        private InputStream reader;

        public FastScanner( InputStream in ) {
            reader = in;
        }

        public int read( ) {
            if ( charsRead == -1 ) {
                throw  new InputMismatchException( );
            }

            if ( currentRead >= charsRead ) {
                currentRead = 0;
                try {
                    charsRead = reader.read( buffer );

                } catch( IOException e ) {
                    throw new InputMismatchException(  );
                }

                if ( charsRead <= 0 ) {
                    return -1;
                }
            }

            return buffer[ currentRead++ ];
        }

        public int nextInt( ) {
            int c = read( );

            while ( isWhitespace( c ) ) {
                c = read( );
            }

            if ( c == -1 ) {
                throw new NullPointerException( );
            } 

            if ( c != '-' && !( c >= '0' && c <= '9' ) ) {
                throw new InputMismatchException( );
            }

            int sign = c == '-' ? -1 : 1;
            if ( sign == -1 ) {
                c = read( );
            }

            if ( c == -1 || !( c >= '0' && c <= '9' ) ) {
                throw new InputMismatchException( );
            }

            int ans = 0;
            while ( !isWhitespace( c )  && c != -1 ) {
                if ( !( c >= '0' && c <= '9' ) ) {
                    throw  new InputMismatchException( );
                }
                int num = c - '0';
                ans = ans * 10 + num;
                c = read( );
            }

            return ans * sign;
        }

        public long nextLong( ) {
            int c = read( );

            while ( isWhitespace( c ) ) {
                c = read( );
            }

            if ( c == -1 ) {
                throw new NullPointerException( );
            }

            if ( c != '-' && !( c >= '0' && c <= '9' ) ) {
                throw new InputMismatchException( );
            }

            int sign = c == '-' ? -1 : 1;
            if ( sign == -1 ) {
                c = read( );
            }

            if ( c == -1 || !( c >= '0' && c <= '9' ) ) {
                throw new InputMismatchException( );
            }

            long ans = 0;
            while ( !isWhitespace( c )  && c != -1 ) {
                if ( !( c >= '0' && c <= '9' ) ) {
                    throw  new InputMismatchException( );
                }
                int num = c - '0';
                ans = ans * 10 + num;
                c = read( );
            }

            return ans * sign;
        }



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

        public String next( ) {
            int c = read( );
            StringBuffer ans = new StringBuffer( );

            while ( isWhitespace( c ) && c != -1 ) {
                c  = read( );
            }

            if ( c == -1 ) {
                return null;
            }

            while ( !isWhitespace( c ) && c != -1 ) {
                ans.appendCodePoint( c );
                c = read( );
            }

            return ans.toString( );

        }

               
        public String nextLine( ) {
            String ans = nextLine0( );

            while ( ans.trim( ).length( ) == 0 ) {
                ans = nextLine0( );
            }

            return ans;
        }
        
        private String nextLine0( ) {
            int c = read( );
            if ( c == -1 ) {
                return null;
            }
            StringBuffer ans = new StringBuffer( );
            while ( c != '\n' && c != '\r' && c != -1 ) {
                ans.appendCodePoint( c );
                c = read( );
            }

            return ans.toString( );

        }


       
        public double nextDouble( ) {
            int c = read( );
            while ( isWhitespace( c ) ) {
                c = read( );
            }

            if ( c == -1 ) {
                throw new NullPointerException( ); 
            }

            if ( c != '.' && c != '-' && !( c >= '0' && c <= '9' ) ) {
                throw new InputMismatchException( );
            }

            int sign = c == '-' ? -1 : 1;
            if ( c == '-' ) {
                c = read( );
            }
            double ans = 0;
            while ( c != -1 && c != '.' && !isWhitespace( c ) ) {
                if ( !( c >= '0' && c <= '9' ) ) {
                    throw new InputMismatchException( );
                }

                int num = c - '0'; 
                ans = ans * 10.0 + num;
                c = read( );
            }

            if ( !isWhitespace( c ) && c != -1 && c != '.' ) {
                throw new InputMismatchException( );
            }

            double pow10 = 1.0;

            if ( c == '.' ) {
                c = read( );
            }

            while ( !isWhitespace( c ) && c != -1 ) {
                pow10 *= 10.0;

                if ( !( c >= '0' && c <= '9' ) ) {
                    throw new InputMismatchException( );
                }
                int num = c - '0';
                ans = ans * 10.0 + num; 
                c = read( );
            }

            return ans * sign / pow10;
        }
    }

}
