// Copyright (c) 2019-present, Facebook, Inc.
// All rights reserved.
//
// This source code is licensed under the license found in the
// LICENSE file in the root directory of this source tree.
//

import java.util. *;
import java.util.stream.*;
import java.lang.*;
import javafx.util.Pair;
public class COUNT_STRINGS_ADJACENT_CHARACTERS_DIFFERENCE_ONE{
static long f_gold ( int n ) {
  long [ ] [ ] dp = new long [ n + 1 ] [ 27 ] ;
  for ( int i = 0 ;
  i < n + 1 ;
  i ++ ) {
    for ( int j = 0 ;
    j < 27 ;
    j ++ ) {
      dp [ i ] [ j ] = 0 ;
    }
  }
  for ( int i = 0 ;
  i <= 25 ;
  i ++ ) {
    dp [ 1 ] [ i ] = 1 ;
  }
  for ( int i = 2 ;
  i <= n ;
  i ++ ) {
    for ( int j = 0 ;
    j <= 25 ;
    j ++ ) {
      if ( j == 0 ) {
        dp [ i ] [ j ] = dp [ i - 1 ] [ j + 1 ] ;
      }
      else {
        dp [ i ] [ j ] = ( dp [ i - 1 ] [ j - 1 ] + dp [ i - 1 ] [ j + 1 ] ) ;
      }
    }
  }
  long sum = 0 ;
  for ( int i = 0 ;
  i <= 25 ;
  i ++ ) {
    sum = ( sum + dp [ n ] [ i ] ) ;
  }
  return sum ;
}
}