public static void main ( String [ ] args ) {
  Scanner scan = new Scanner ( System . in ) ;
  int n = scan . nextInt ( ) ;
  int [ ] open = new int [ 1000 ] ;
  ArrayList < Integer > same = new ArrayList < > ( ) ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) {
    int a = scan . nextInt ( ) ;
    int b = scan . nextInt ( ) ;
    if ( same . contains ( a ) ) {
      open [ b - 1 ] += 1000 ;
      open [ a - 1 ] -- ;
    }
    if ( a == b ) {
      if ( ! same . contains ( b ) ) {
        same . add ( b ) ;
        if ( open [ a - 1 ] % 1000 > 0 ) {
          open [ a - 1 ] -= open [ a - 1 ] % 1000 ;
        }
      }
    }
    else open [ b - 1 ] += 1000 ;
    open [ a - 1 ] ++ ;
  }
  int countC = 0 ;
  for ( int i = 0 ;
  i < 1000 ;
  i ++ ) {
    if ( open [ i ] > 0 && open [ i ] < 1000 ) countC += open [ i ] ;
  }
  System . out . println ( countC ) ;
}

public static void main ( String [ ] args ) { Scanner scan = new Scanner ( System . in ) ; int n = scan . nextInt ( ) ; int [ ] open = new int [ 1000 ] ; ArrayList < Integer > same = new ArrayList < > ( ) ; for ( int i = 0 ; i < n ; i ++ ) { int a = scan . nextInt ( ) ; int b = scan . nextInt ( ) ; if ( same . contains ( a ) ) { open [ b - 1 ] += 1000 ; open [ a - 1 ] -- ; } if ( a == b ) { if ( ! same . contains ( b ) ) { same . add ( b ) ; if ( open [ a - 1 ] % 1000 > 0 ) { open [ a - 1 ] -= open [ a - 1 ] % 1000 ; } } } else open [ b - 1 ] += 1000 ; open [ a - 1 ] ++ ; } int countC = 0 ; for ( int i = 0 ; i < 1000 ; i ++ ) { if ( open [ i ] > 0 && open [ i ] < 1000 ) countC += open [ i ] ; } System . out . println ( countC ) ; }
(method_declaration (modifiers) type: (void_type) name: (identifier) parameters: (formal_parameters (formal_parameter type: (array_type element: (type_identifier) dimensions: (dimensions)) name: (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: (integral_type) dimensions: (dimensions)) declarator: (variable_declarator name: (identifier) value: (array_creation_expression type: (integral_type) dimensions: (dimensions_expr (decimal_integer_literal))))) (local_variable_declaration type: (generic_type (type_identifier) (type_arguments (type_identifier))) declarator: (variable_declarator name: (identifier) value: (object_creation_expression type: (generic_type (type_identifier) (type_arguments)) arguments: (argument_list)))) (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 (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: (integral_type) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))) (if_statement condition: (parenthesized_expression (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier)))) consequence: (block (expression_statement (assignment_expression left: (array_access array: (identifier) index: (binary_expression left: (identifier) right: (decimal_integer_literal))) right: (decimal_integer_literal))) (expression_statement (update_expression (array_access array: (identifier) index: (binary_expression left: (identifier) right: (decimal_integer_literal))))))) (if_statement condition: (parenthesized_expression (binary_expression left: (identifier) right: (identifier))) consequence: (block (if_statement condition: (parenthesized_expression (unary_expression operand: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier))))) consequence: (block (expression_statement (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier)))) (if_statement condition: (parenthesized_expression (binary_expression left: (binary_expression left: (array_access array: (identifier) index: (binary_expression left: (identifier) right: (decimal_integer_literal))) right: (decimal_integer_literal)) right: (decimal_integer_literal))) consequence: (block (expression_statement (assignment_expression left: (array_access array: (identifier) index: (binary_expression left: (identifier) right: (decimal_integer_literal))) right: (binary_expression left: (array_access array: (identifier) index: (binary_expression left: (identifier) right: (decimal_integer_literal))) right: (decimal_integer_literal))))))))) alternative: (expression_statement (assignment_expression left: (array_access array: (identifier) index: (binary_expression left: (identifier) right: (decimal_integer_literal))) right: (decimal_integer_literal)))) (expression_statement (update_expression (array_access array: (identifier) index: (binary_expression left: (identifier) right: (decimal_integer_literal))))))) (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: (decimal_integer_literal)) update: (update_expression (identifier)) body: (block (if_statement condition: (parenthesized_expression (binary_expression left: (binary_expression left: (array_access array: (identifier) index: (identifier)) right: (decimal_integer_literal)) right: (binary_expression left: (array_access array: (identifier) index: (identifier)) right: (decimal_integer_literal)))) consequence: (expression_statement (assignment_expression left: (identifier) right: (array_access array: (identifier) index: (identifier))))))) (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (identifier))))))