public static void main ( String [ ] args ) {
  Scanner sc = new Scanner ( System . in ) ;
  int n = sc . nextInt ( ) ;
  String arr [ ] [ ] = new String [ n ] [ n ] ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) {
    arr [ i ] = sc . next ( ) . split ( "" ) ;
  }
  String standard1 = arr [ 0 ] [ 0 ] ;
  String standard2 = arr [ 0 ] [ 1 ] ;
  if ( standard1 . equals ( standard2 ) ) {
    System . out . println ( "NO" ) ;
    return ;
  }
  int wide = n / 2 ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) {
    if ( ! ( arr [ i ] [ i ] . equals ( standard1 ) & arr [ i ] [ n - i - 1 ] . equals ( standard1 ) ) ) {
      System . out . println ( "NO" ) ;
      return ;
    }
    for ( int j = 0 ;
    j < n ;
    j ++ ) {
      if ( j != i & j != n - i - 1 ) {
        if ( ! arr [ i ] [ j ] . equals ( standard2 ) ) {
          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 ( ) ; String arr [ ] [ ] = new String [ n ] [ n ] ; for ( int i = 0 ; i < n ; i ++ ) { arr [ i ] = sc . next ( ) . split ( " " ) ; } String standard1 = arr [ 0 ] [ 0 ] ; String standard2 = arr [ 0 ] [ 1 ] ; if ( standard1 . equals ( standard2 ) ) { System . out . println ( " NO " ) ; return ; } int wide = n / 2 ; for ( int i = 0 ; i < n ; i ++ ) { if ( ! ( arr [ i ] [ i ] . equals ( standard1 ) & arr [ i ] [ n - i - 1 ] . equals ( standard1 ) ) ) { System . out . println ( " NO " ) ; return ; } for ( int j = 0 ; j < n ; j ++ ) { if ( j != i & j != n - i - 1 ) { if ( ! arr [ i ] [ j ] . equals ( standard2 ) ) { System . out . println ( " NO " ) ; return ; } } } } System . out . println ( " YES " ) ; }
(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: (type_identifier) declarator: (variable_declarator name: (identifier) dimensions: (dimensions) value: (array_creation_expression type: (type_identifier) dimensions: (dimensions_expr (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: (block (expression_statement (assignment_expression left: (array_access array: (identifier) index: (identifier)) right: (method_invocation object: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)) name: (identifier) arguments: (argument_list (string_literal))))))) (local_variable_declaration type: (type_identifier) declarator: (variable_declarator name: (identifier) value: (array_access array: (array_access array: (identifier) index: (decimal_integer_literal)) index: (decimal_integer_literal)))) (local_variable_declaration type: (type_identifier) declarator: (variable_declarator name: (identifier) value: (array_access array: (array_access array: (identifier) index: (decimal_integer_literal)) index: (decimal_integer_literal)))) (if_statement condition: (parenthesized_expression (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier)))) consequence: (block (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (string_literal)))) (return_statement))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (binary_expression left: (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: (block (if_statement condition: (parenthesized_expression (unary_expression operand: (parenthesized_expression (binary_expression left: (method_invocation object: (array_access array: (array_access array: (identifier) index: (identifier)) index: (identifier)) name: (identifier) arguments: (argument_list (identifier))) right: (method_invocation object: (array_access array: (array_access array: (identifier) index: (identifier)) index: (binary_expression left: (binary_expression left: (identifier) right: (identifier)) right: (decimal_integer_literal))) name: (identifier) arguments: (argument_list (identifier))))))) consequence: (block (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (string_literal)))) (return_statement))) (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: (binary_expression left: (identifier) right: (identifier)) right: (binary_expression left: (identifier) right: (binary_expression left: (binary_expression left: (identifier) right: (identifier)) right: (decimal_integer_literal))))) consequence: (block (if_statement condition: (parenthesized_expression (unary_expression operand: (method_invocation object: (array_access array: (array_access array: (identifier) index: (identifier)) index: (identifier)) name: (identifier) arguments: (argument_list (identifier))))) 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))))))