public static void main ( String [ ] args ) {
  Scanner scan = new Scanner ( System . in ) ;
  int n = scan . nextInt ( ) , d = scan . nextInt ( ) ;
  int a [ ] = new int [ n + 1 ] ;
  for ( int i = 1 ;
  i <= n ;
  i ++ ) a [ i ] = scan . nextInt ( ) ;
  int ans = 0 ;
  for ( int i = 2 ;
  i <= n ;
  i ++ ) {
    if ( a [ i ] <= a [ i - 1 ] ) {
      ans += ( a [ i - 1 ] - a [ i ] ) / d + 1 ;
      a [ i ] += ( ( a [ i - 1 ] - a [ i ] ) / d + 1 ) * d ;
    }
  }
  System . out . print ( ans ) ;
}

public static void main ( String [ ] args ) { Scanner scan = new Scanner ( System . in ) ; int n = scan . nextInt ( ) , d = scan . nextInt ( ) ; int a [ ] = new int [ n + 1 ] ; for ( int i = 1 ; i <= n ; i ++ ) a [ i ] = scan . nextInt ( ) ; int ans = 0 ; for ( int i = 2 ; i <= n ; i ++ ) { if ( a [ i ] <= a [ i - 1 ] ) { ans += ( a [ i - 1 ] - a [ i ] ) / d + 1 ; a [ i ] += ( ( a [ i - 1 ] - a [ i ] ) / d + 1 ) * d ; } } System . out . print ( ans ) ; }
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