public static void main ( String [ ] args ) {
  Scanner sc = new Scanner ( System . in ) ;
  int n = sc . nextInt ( ) ;
  int [ ] [ ] a = new int [ n ] [ n ] ;
  sc . nextLine ( ) ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) {
    String s = sc . nextLine ( ) . trim ( ) ;
    for ( int j = 0 ;
    j < n ;
    j ++ ) {
      if ( s . charAt ( j ) == '#' ) a [ i ] [ j ] = 1 ;
      else a [ i ] [ j ] = 0 ;
    }
  }
  for ( int i = 1 ;
  i < n - 1 ;
  i ++ ) {
    for ( int j = 1 ;
    j < n - 1 ;
    j ++ ) {
      if ( a [ i ] [ j ] == 0 ) {
        if ( a [ i - 1 ] [ j ] == 0 && a [ i + 1 ] [ j ] == 0 && a [ i ] [ j + 1 ] == 0 && a [ i ] [ j - 1 ] == 0 ) {
          a [ i - 1 ] [ j ] = a [ i + 1 ] [ j ] = a [ i ] [ j - 1 ] = a [ i ] [ j + 1 ] = a [ i ] [ j ] = 1 ;
        }
      }
    }
  }
  for ( int i = 0 ;
  i < n ;
  i ++ ) for ( int j = 0 ;
  j < n ;
  j ++ ) {
    if ( a [ i ] [ j ] == 0 ) {
      System . out . println ( "NO" ) ;
      return ;
    }
  }
  System . out . println ( "YES" ) ;
}

public static void main ( String [ ] args ) { Scanner sc = new Scanner ( System . in ) ; int n = sc . nextInt ( ) ; int [ ] [ ] a = new int [ n ] [ n ] ; sc . nextLine ( ) ; for ( int i = 0 ; i < n ; i ++ ) { String s = sc . nextLine ( ) . trim ( ) ; for ( int j = 0 ; j < n ; j ++ ) { if ( s . charAt ( j ) == ' # ' ) a [ i ] [ j ] = 1 ; else a [ i ] [ j ] = 0 ; } } for ( int i = 1 ; i < n - 1 ; i ++ ) { for ( int j = 1 ; j < n - 1 ; j ++ ) { if ( a [ i ] [ j ] == 0 ) { if ( a [ i - 1 ] [ j ] == 0 && a [ i + 1 ] [ j ] == 0 && a [ i ] [ j + 1 ] == 0 && a [ i ] [ j - 1 ] == 0 ) { a [ i - 1 ] [ j ] = a [ i + 1 ] [ j ] = a [ i ] [ j - 1 ] = a [ i ] [ j + 1 ] = a [ i ] [ j ] = 1 ; } } } } for ( int i = 0 ; i < n ; i ++ ) for ( int j = 0 ; j < n ; j ++ ) { if ( a [ i ] [ j ] == 0 ) { System . out . println ( " NO " ) ; return ; } } System . out . println ( " YES " ) ; }
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(method_invocation object: (identifier) name: (identifier) 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: (type_identifier) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)) name: (identifier) 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 (if_statement condition: (parenthesized_expression (binary_expression left: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier))) right: (character_literal))) consequence: (expression_statement (assignment_expression left: (array_access array: (array_access array: (identifier) index: (identifier)) index: (identifier)) right: (decimal_integer_literal))) alternative: (expression_statement (assignment_expression left: (array_access array: (array_access array: (identifier) index: (identifier)) index: (identifier)) right: (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: (binary_expression left: (identifier) right: (decimal_integer_literal))) update: (update_expression (identifier)) body: (block (for_statement init: (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) condition: (binary_expression left: (identifier) right: (binary_expression left: (identifier) right: (decimal_integer_literal))) update: (update_expression (identifier)) body: (block (if_statement condition: (parenthesized_expression (binary_expression left: (array_access array: (array_access array: (identifier) index: (identifier)) index: (identifier)) right: (decimal_integer_literal))) consequence: (block (if_statement condition: (parenthesized_expression (binary_expression left: (binary_expression left: (binary_expression left: (binary_expression left: (array_access array: (array_access array: (identifier) index: (binary_expression left: (identifier) right: (decimal_integer_literal))) index: (identifier)) right: (decimal_integer_literal)) right: (binary_expression left: (array_access array: (array_access array: (identifier) index: (binary_expression left: (identifier) right: (decimal_integer_literal))) index: (identifier)) right: (decimal_integer_literal))) right: (binary_expression left: (array_access array: (array_access array: (identifier) index: (identifier)) index: (binary_expression left: (identifier) right: (decimal_integer_literal))) right: (decimal_integer_literal))) right: (binary_expression left: (array_access array: (array_access array: (identifier) index: (identifier)) index: (binary_expression left: (identifier) right: (decimal_integer_literal))) right: (decimal_integer_literal)))) consequence: (block (expression_statement (assignment_expression left: (array_access array: (array_access array: (identifier) index: (binary_expression left: (identifier) right: (decimal_integer_literal))) index: (identifier)) right: (assignment_expression left: (array_access array: (array_access array: (identifier) index: (binary_expression left: (identifier) right: (decimal_integer_literal))) index: (identifier)) right: (assignment_expression left: (array_access array: (array_access array: (identifier) index: (identifier)) index: (binary_expression left: (identifier) right: (decimal_integer_literal))) right: (assignment_expression left: (array_access array: (array_access array: (identifier) index: (identifier)) index: (binary_expression left: (identifier) right: (decimal_integer_literal))) right: (assignment_expression left: (array_access array: (array_access array: (identifier) index: (identifier)) index: (identifier)) right: (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: (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 (binary_expression left: (array_access array: (array_access array: (identifier) index: (identifier)) index: (identifier)) right: (decimal_integer_literal))) consequence: (block (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (string_literal)))) (return_statement)))))) (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (string_literal))))))