# coding: utf-8
# Your code here!
n = int(input())

cnt = 0

for i in range(10, min(100, n + 1)):
    cnt = cnt + 1 if (int(str(i)[0]) + int(str(i)[1])) % 3 == 0 and i % 3 == 0 else cnt
    
if n > 100:
    numList = ['0', '3', '6', '9']
    for j in range(4 ** len(str(n))):
        st = ''
        q = j
        for k in range(len(str(n))):
            st += numList[q % 4]
            q = (q - q % 4) // 4
        s = int(st)
        if s <= n and s > 100:
            cnt += 1
    
print(cnt)