from collections import deque

n = int(input())
ans = min(100,n)//3 - 10//3

d = deque()
for i in [3,6,9]:
    for j in [0,3,6,9]:
        d.append(i*10+j)

while(True):
    i = d.popleft()
    for j in [0,3,6,9]:
        x = i*10+j
        if(x > n):
            print(ans)
            exit()
        ans += 1
        d.append(x)