public static void main ( String [ ] args ) {
  try {
    FastScanner in = new FastScanner ( ) ;
    PrintWriter out = new PrintWriter ( System . out ) ;
    int n = in . nextInt ( ) ;
    int k = in . nextInt ( ) ;
    int A [ ] = in . readArray ( n ) ;
    int ct = 0 ;
    int ptr = 100000 ;
    while ( ptr -- > 0 ) {
      boolean flag = false ;
      int prev = k ;
      for ( int i = n - 1 ;
      i >= 0 ;
      i -- ) {
        if ( A [ i ] >= k ) continue ;
        flag = true ;
        if ( A [ i ] != prev ) {
          prev = A [ i ] ;
          A [ i ] ++ ;
        }
      }
      if ( flag ) ct ++ ;
      else break ;
    }
    System . out . println ( ct ) ;
    out . flush ( ) ;
    out . close ( ) ;
  }
  catch ( Exception e ) {
    return ;
  }
}

public static void main ( String [ ] args ) { try { FastScanner in = new FastScanner ( ) ; PrintWriter out = new PrintWriter ( System . out ) ; int n = in . nextInt ( ) ; int k = in . nextInt ( ) ; int A [ ] = in . readArray ( n ) ; int ct = 0 ; int ptr = 100000 ; while ( ptr -- > 0 ) { boolean flag = false ; int prev = k ; for ( int i = n - 1 ; i >= 0 ; i -- ) { if ( A [ i ] >= k ) continue ; flag = true ; if ( A [ i ] != prev ) { prev = A [ i ] ; A [ i ] ++ ; } } if ( flag ) ct ++ ; else break ; } System . out . println ( ct ) ; out . flush ( ) ; out . close ( ) ; } catch ( Exception e ) { return ; } }
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