public static void main ( String [ ] args ) {
  Scanner sc = new Scanner ( System . in ) ;
  int n = sc . nextInt ( ) ;
  int k = sc . nextInt ( ) ;
  int [ ] a = new int [ 101 ] ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) a [ sc . nextInt ( ) ] ++ ;
  int count = 0 ;
  while ( a [ k ] != n ) {
    for ( int i = k - 1 ;
    i > 0 ;
    i -- ) {
      if ( a [ i ] > 0 ) {
        a [ i ] -- ;
        a [ i + 1 ] ++ ;
      }
    }
    count ++ ;
  }
  System . out . println ( count ) ;
  sc . close ( ) ;
}

public static void main ( String [ ] args ) { Scanner sc = new Scanner ( System . in ) ; int n = sc . nextInt ( ) ; int k = sc . nextInt ( ) ; int [ ] a = new int [ 101 ] ; for ( int i = 0 ; i < n ; i ++ ) a [ sc . nextInt ( ) ] ++ ; int count = 0 ; while ( a [ k ] != n ) { for ( int i = k - 1 ; i > 0 ; i -- ) { if ( a [ i ] > 0 ) { a [ i ] -- ; a [ i + 1 ] ++ ; } } count ++ ; } System . out . println ( count ) ; sc . close ( ) ; }
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