public static void main ( String [ ] args ) throws Exception {
  Scanner sc = new Scanner ( System . in ) ;
  int n = sc . nextInt ( ) ;
  Point [ ] p = new Point [ n ] ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) p [ i ] = new Point ( sc . nextInt ( ) , sc . nextInt ( ) ) ;
  vis = new boolean [ n ] ;
  int count = 0 ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) {
    if ( ! vis [ i ] ) {
      dfs ( i , n , p ) ;
      count ++ ;
    }
  }
  System . out . println ( count - 1 ) ;
}

public static void main ( String [ ] args ) throws Exception { Scanner sc = new Scanner ( System . in ) ; int n = sc . nextInt ( ) ; Point [ ] p = new Point [ n ] ; for ( int i = 0 ; i < n ; i ++ ) p [ i ] = new Point ( sc . nextInt ( ) , sc . nextInt ( ) ) ; vis = new boolean [ n ] ; int count = 0 ; for ( int i = 0 ; i < n ; i ++ ) { if ( ! vis [ i ] ) { dfs ( i , n , p ) ; count ++ ; } } System . out . println ( count - 1 ) ; }
(method_declaration (modifiers) type: (void_type) name: (identifier) parameters: (formal_parameters (formal_parameter type: (array_type element: (type_identifier) dimensions: (dimensions)) name: (identifier))) (throws (type_identifier)) body: (block (local_variable_declaration type: (type_identifier) declarator: (variable_declarator name: (identifier) value: (object_creation_expression type: (type_identifier) arguments: (argument_list (field_access object: (identifier) field: (identifier)))))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))) (local_variable_declaration type: (array_type element: (type_identifier) dimensions: (dimensions)) declarator: (variable_declarator name: (identifier) value: (array_creation_expression type: (type_identifier) dimensions: (dimensions_expr (identifier))))) (for_statement init: (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) condition: (binary_expression left: (identifier) right: (identifier)) update: (update_expression (identifier)) body: (expression_statement (assignment_expression left: (array_access array: (identifier) index: (identifier)) right: (object_creation_expression type: (type_identifier) arguments: (argument_list (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)) (method_invocation object: (identifier) name: (identifier) arguments: (argument_list))))))) (expression_statement (assignment_expression left: (identifier) right: (array_creation_expression type: (boolean_type) dimensions: (dimensions_expr (identifier))))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) (for_statement init: (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) condition: (binary_expression left: (identifier) right: (identifier)) update: (update_expression (identifier)) body: (block (if_statement condition: (parenthesized_expression (unary_expression operand: (array_access array: (identifier) index: (identifier)))) consequence: (block (expression_statement (method_invocation name: (identifier) arguments: (argument_list (identifier) (identifier) (identifier)))) (expression_statement (update_expression (identifier))))))) (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (binary_expression left: (identifier) right: (decimal_integer_literal)))))))