public static void main ( String [ ] args ) {
  Scanner in = new Scanner ( System . in ) ;
  int n = in . nextInt ( ) ;
  String board [ ] = new String [ n ] ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) {
    board [ i ] = in . next ( ) ;
  }
  boolean ok = true ;
  char l1 = board [ 0 ] . charAt ( 0 ) ;
  char l2 = board [ 0 ] . charAt ( 1 ) ;
  if ( l1 == l2 ) {
    ok = false ;
  }
  for ( int i = 0 ;
  i < n ;
  i ++ ) {
    for ( int j = 0 ;
    j < n ;
    j ++ ) {
      if ( i == j || i == ( n - j - 1 ) ) {
        if ( board [ i ] . charAt ( j ) != l1 ) {
          ok = false ;
        }
      }
      else {
        if ( board [ i ] . charAt ( j ) != l2 ) {
          ok = false ;
        }
      }
    }
  }
  System . out . println ( ok ? "YES" : "NO" ) ;
}

public static void main ( String [ ] args ) { Scanner in = new Scanner ( System . in ) ; int n = in . nextInt ( ) ; String board [ ] = new String [ n ] ; for ( int i = 0 ; i < n ; i ++ ) { board [ i ] = in . next ( ) ; } boolean ok = true ; char l1 = board [ 0 ] . charAt ( 0 ) ; char l2 = board [ 0 ] . charAt ( 1 ) ; if ( l1 == l2 ) { ok = false ; } for ( int i = 0 ; i < n ; i ++ ) { for ( int j = 0 ; j < n ; j ++ ) { if ( i == j || i == ( n - j - 1 ) ) { if ( board [ i ] . charAt ( j ) != l1 ) { ok = false ; } } else { if ( board [ i ] . charAt ( j ) != l2 ) { ok = false ; } } } } System . out . println ( ok ? " YES " : " NO " ) ; }
(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))))) (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: (boolean_type) declarator: (variable_declarator name: (identifier) value: (true))) (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: (block (expression_statement (assignment_expression left: (identifier) right: (false))))) (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: (parenthesized_expression (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)))))) 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))))))))))) (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (ternary_expression condition: (identifier) consequence: (string_literal) alternative: (string_literal)))))))