Problem:
Score : 300 points

Problem Statement

You are given an integer N. Among the integers between 1 and N (inclusive), how many Shichi-Go-San numbers (literally "Seven-Five-Three numbers") are there?

Here, a Shichi-Go-San number is a positive integer that satisfies the following condition:

When the number is written in base ten, each of the digits 7, 5 and 3 appears at least once, and the other digits never appear.

Constraints

1 \leq N < 10^9

N is an integer.

Input

Input is given from Standard Input in the following format:

N

Output

Print the number of the Shichi-Go-San numbers between 1 and N (inclusive).

Sample Input 1

575

Sample Output 1

4

There are four Shichi-Go-San numbers not greater than 575: 357, 375, 537 and 573.

Sample Input 2

3600

Sample Output 2

13

There are 13 Shichi-Go-San numbers not greater than 3600: the above four numbers, 735, 753, 3357, 3375, 3537, 3557, 3573, 3575 and 3577.

Sample Input 3

999999999

Sample Output 3

26484

Solution in OCaml (4.02.3) (judge verdict: Accepted)

let n = read_int ()
let f m = let cs = Array.make 8 0 in let rec f n =
  if n = 0 then cs.(3) + cs.(5) + cs.(7) = 3 else (cs.(n mod 10) <- 1; f (n / 10)) in m <= n && f m
let rec g m = if m > n then 0 else List.fold_left (fun c k -> c + g (10 * m + k) + if f @@ 10 * m + k then 1 else 0) 0 [3; 5; 7]
let _ = g 0 |> Printf.printf "%d\n"