public static void main ( String [ ] args ) {
  FastScanner scanner = new FastScanner ( ) ;
  int k = scanner . nextInt ( ) ;
  String N = scanner . next ( ) ;
  int L = N . length ( ) , total = 0 , current = 0 ;
  int count [ ] = new int [ 15 ] ;
  for ( int idx = 0 ;
  idx < N . length ( ) ;
  ++ idx ) {
    count [ N . charAt ( idx ) - '0' ] ++ ;
    current += N . charAt ( idx ) - '0' ;
  }
  for ( int digit = 0 , avail , req , take ;
  digit < 10 && current < k ;
  ++ digit ) {
    avail = count [ digit ] ;
    req = ( k - current + 8 - digit ) / ( 9 - digit ) ;
    take = Math . min ( avail , req ) ;
    total += take ;
    current += take * ( 9 - digit ) ;
  }
  System . out . println ( total ) ;
  return ;
}

public static void main ( String [ ] args ) { FastScanner scanner = new FastScanner ( ) ; int k = scanner . nextInt ( ) ; String N = scanner . next ( ) ; int L = N . length ( ) , total = 0 , current = 0 ; int count [ ] = new int [ 15 ] ; for ( int idx = 0 ; idx < N . length ( ) ; ++ idx ) { count [ N . charAt ( idx ) - '0' ] ++ ; current += N . charAt ( idx ) - '0' ; } for ( int digit = 0 , avail , req , take ; digit < 10 && current < k ; ++ digit ) { avail = count [ digit ] ; req = ( k - current + 8 - digit ) / ( 9 - digit ) ; take = Math . min ( avail , req ) ; total += take ; current += take * ( 9 - digit ) ; } System . out . println ( total ) ; return ; }
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