public static void main ( String [ ] args ) {
  Scanner input = new Scanner ( System . in ) ;
  int n = input . nextInt ( ) ;
  String [ ] str = new String [ n ] ;
  boolean flag = true ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) {
    str [ i ] = input . next ( ) ;
  }
  char diagonalLetter = str [ 0 ] . charAt ( 0 ) ;
  char secondLetter = str [ 0 ] . charAt ( 1 ) ;
  if ( diagonalLetter == secondLetter ) flag = false ;
  else {
    for ( int i = 0 ;
    i < n ;
    i ++ ) {
      for ( int j = 0 ;
      j < n ;
      j ++ ) {
        if ( i == j || j == n - i - 1 ) {
          if ( str [ i ] . charAt ( j ) != diagonalLetter ) {
            flag = false ;
            break ;
          }
        }
        else {
          if ( str [ i ] . charAt ( j ) != secondLetter ) {
            flag = false ;
            break ;
          }
        }
      }
      if ( ! flag ) break ;
    }
  }
  if ( flag ) System . out . println ( "YES" ) ;
  else System . out . println ( "NO" ) ;
  input . close ( ) ;
}

public static void main ( String [ ] args ) { Scanner input = new Scanner ( System . in ) ; int n = input . nextInt ( ) ; String [ ] str = new String [ n ] ; boolean flag = true ; for ( int i = 0 ; i < n ; i ++ ) { str [ i ] = input . next ( ) ; } char diagonalLetter = str [ 0 ] . charAt ( 0 ) ; char secondLetter = str [ 0 ] . charAt ( 1 ) ; if ( diagonalLetter == secondLetter ) flag = false ; else { for ( int i = 0 ; i < n ; i ++ ) { for ( int j = 0 ; j < n ; j ++ ) { if ( i == j || j == n - i - 1 ) { if ( str [ i ] . charAt ( j ) != diagonalLetter ) { flag = false ; break ; } } else { if ( str [ i ] . charAt ( j ) != secondLetter ) { flag = false ; break ; } } } if ( ! flag ) break ; } } if ( flag ) System . out . println ( " YES " ) ; else System . out . println ( " NO " ) ; input . close ( ) ; }
(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: (type_identifier) dimensions: (dimensions)) declarator: (variable_declarator name: (identifier) value: (array_creation_expression type: (type_identifier) dimensions: (dimensions_expr (identifier))))) (local_variable_declaration type: (boolean_type) declarator: (variable_declarator name: (identifier) value: (true))) (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: (identifier) name: (identifier) arguments: (argument_list)))))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (array_access array: (identifier) index: (decimal_integer_literal)) name: (identifier) arguments: (argument_list (decimal_integer_literal))))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (array_access array: (identifier) index: (decimal_integer_literal)) name: (identifier) arguments: (argument_list (decimal_integer_literal))))) (if_statement condition: (parenthesized_expression (binary_expression left: (identifier) right: (identifier))) consequence: (expression_statement (assignment_expression left: (identifier) right: (false))) alternative: (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: (identifier)) 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: (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 (binary_expression left: (method_invocation object: (array_access array: (identifier) index: (identifier)) name: (identifier) arguments: (argument_list (identifier))) right: (identifier))) consequence: (block (expression_statement (assignment_expression left: (identifier) right: (false))) (break_statement)))) alternative: (block (if_statement condition: (parenthesized_expression (binary_expression left: (method_invocation object: (array_access array: (identifier) index: (identifier)) name: (identifier) arguments: (argument_list (identifier))) right: (identifier))) consequence: (block (expression_statement (assignment_expression left: (identifier) right: (false))) (break_statement))))))) (if_statement condition: (parenthesized_expression (unary_expression operand: (identifier))) consequence: (break_statement)))))) (if_statement condition: (parenthesized_expression (identifier)) consequence: (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (string_literal)))) alternative: (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (string_literal))))) (expression_statement (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))))