# coding: utf-8
import itertools
N = input()
ans = 0

for i in range(3, len(N)+1):
    for ptn in itertools.product((3,5,7), repeat=i):
        if (3 not in ptn) or (5 not in ptn) or (7 not in ptn):
            continue
        a = int("".join(list(map(str, ptn))))
        if a <= N:
            ans += 1
print(ans)