from collections import deque
n = int(input())
q = deque()
q.append('')
res = set()
while q:
    m = q.pop_front()
    for c in '357':
        if int(m+c) > n: continue
        q.append(m+c)
    for c in '357':
        if c not in m: break
    else:
        res.add(m)
print(len(res))