public static void main ( String [ ] args ) {
  FastScanner sc = new FastScanner ( ) ;
  int n = sc . nextInt ( ) ;
  Long a [ ] = sc . readArray ( n ) ;
  Long maxi = 0L , ans = 0L ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) {
    maxi = Math . max ( maxi , a [ i ] ) ;
    a [ i ] = maxi - a [ i ] ;
  }
  Long prev = 0L ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) if ( a [ i ] >= prev ) prev = a [ i ] ;
  else {
    ans += prev - a [ i ] ;
    prev = a [ i ] ;
  }
  System . out . println ( ans + prev ) ;
}

public static void main ( String [ ] args ) { FastScanner sc = new FastScanner ( ) ; int n = sc . nextInt ( ) ; Long a [ ] = sc . readArray ( n ) ; Long maxi = 0L , ans = 0L ; for ( int i = 0 ; i < n ; i ++ ) { maxi = Math . max ( maxi , a [ i ] ) ; a [ i ] = maxi - a [ i ] ; } Long prev = 0L ; for ( int i = 0 ; i < n ; i ++ ) if ( a [ i ] >= prev ) prev = a [ i ] ; else { ans += prev - a [ i ] ; prev = a [ i ] ; } System . out . println ( ans + prev ) ; }
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