public static void main ( String [ ] args ) {
  FastScanner input = new FastScanner ( ) ;
  int k = input . nextInt ( ) ;
  char s [ ] = input . next ( ) . toCharArray ( ) ;
  int sum = SumOfDigits ( s ) ;
  if ( sum >= k ) {
    System . out . println ( "0" ) ;
    return ;
  }
  Arrays . sort ( s ) ;
  int count = 0 ;
  for ( int i = 0 ;
  i < s . length ;
  i ++ ) {
    int ch = s [ i ] - '0' ;
    if ( ch != 9 ) {
      sum -= ch ;
      sum += 9 ;
      count ++ ;
      if ( sum >= k ) {
        System . out . println ( count ) ;
        return ;
      }
    }
  }
}

public static void main ( String [ ] args ) { FastScanner input = new FastScanner ( ) ; int k = input . nextInt ( ) ; char s [ ] = input . next ( ) . toCharArray ( ) ; int sum = SumOfDigits ( s ) ; if ( sum >= k ) { System . out . println ( "0" ) ; return ; } Arrays . sort ( s ) ; int count = 0 ; for ( int i = 0 ; i < s . length ; i ++ ) { int ch = s [ i ] - '0' ; if ( ch != 9 ) { sum -= ch ; sum += 9 ; count ++ ; if ( sum >= k ) { System . out . println ( count ) ; return ; } } } }
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