# 1桁はない、2桁では3の倍数すべて12-99
# 3桁以上では、全桁が0369のどれか

N = int(input())

import sys
sys.setrecursionlimit(10**7)

def dfs(num):
    if 100 <= num <= N:
        nums.append(num)
    
    if num*10+0 <= N:
        dfs(num*10+0)
    if num*10+3 <= N:
        dfs(num*10+3)
    if num*10+6 <= N:
        dfs(num*10+6)
    if num*10+9 <= N:
        dfs(num*10+9)
        
nums = []
dfs(3)
dfs(6)
dfs(9)
nums.sort()
#print(nums)

if N <= 100:
    ans = N//3 - 10//3
else:
    ans = 100//3-10//3
    ans += len(nums)
print(ans)