public static void main ( String [ ] args ) {
  Scanner scanner = new Scanner ( System . in ) ;
  int n = Integer . parseInt ( scanner . nextLine ( ) ) ;
  String [ ] line = scanner . nextLine ( ) . split ( " " , n ) ;
  int [ ] arr = new int [ n ] ;
  int total = 0 ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) {
    arr [ i ] = Integer . parseInt ( line [ i ] ) ;
    total += arr [ i ] ;
  }
  if ( total % n != 0 ) {
    System . out . println ( - 1 ) ;
    return ;
  }
  int bridges = 0 ;
  int avg = total / n ;
  int currentTotal = 0 ;
  int currentSize = 0 ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) {
    if ( ( currentTotal + arr [ i ] ) == avg * ( currentSize + 1 ) ) {
      currentTotal = 0 ;
      currentSize = 0 ;
    }
    else {
      currentTotal += arr [ i ] ;
      currentSize ++ ;
      bridges ++ ;
    }
  }
  System . out . println ( bridges ) ;
}

public static void main ( String [ ] args ) { Scanner scanner = new Scanner ( System . in ) ; int n = Integer . parseInt ( scanner . nextLine ( ) ) ; String [ ] line = scanner . nextLine ( ) . split ( " ▁ " , n ) ; int [ ] arr = new int [ n ] ; int total = 0 ; for ( int i = 0 ; i < n ; i ++ ) { arr [ i ] = Integer . parseInt ( line [ i ] ) ; total += arr [ i ] ; } if ( total % n != 0 ) { System . out . println ( - 1 ) ; return ; } int bridges = 0 ; int avg = total / n ; int currentTotal = 0 ; int currentSize = 0 ; for ( int i = 0 ; i < n ; i ++ ) { if ( ( currentTotal + arr [ i ] ) == avg * ( currentSize + 1 ) ) { currentTotal = 0 ; currentSize = 0 ; } else { currentTotal += arr [ i ] ; currentSize ++ ; bridges ++ ; } } System . out . println ( bridges ) ; }
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