from decimal import Decimal

N = Decimal(input().strip())
count = 0
i = 12
while i <= N:
    if i < 100:
        count += 1
    else:
        s = str(i).replace('0', '')\
            .replace('3', '')\
            .replace('6', '')\
            .replace('9', '')
        if s == '':
            count += 1

    i += 3

print(count)