public static void main ( String [ ] args ) {
  Scanner in = new Scanner ( System . in ) ;
  int n = in . nextInt ( ) ;
  int unrated = 0 ;
  int police = 0 ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) {
    int x = in . nextInt ( ) ;
    if ( x != - 1 ) {
      police += x ;
      continue ;
    }
    if ( police == 0 ) unrated ++ ;
    else police -- ;
  }
  System . out . println ( unrated ) ;
}

public static void main ( String [ ] args ) { Scanner in = new Scanner ( System . in ) ; int n = in . nextInt ( ) ; int unrated = 0 ; int police = 0 ; for ( int i = 0 ; i < n ; i ++ ) { int x = in . nextInt ( ) ; if ( x != - 1 ) { police += x ; continue ; } if ( police == 0 ) unrated ++ ; else police -- ; } System . out . println ( unrated ) ; }
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