from itertools import product
N=int(input())

#2桁の完全な3の倍数
S=set(range(12,100,3))

#3桁以上の完全な3の倍数を追加
P=product(["3","6","9","0","",],repeat=max(3,len(str(N))))
for X in P:
    T=""
    for a in X:
        T+=a
    if len(T)>=3 and T[0]!="0":
        S.add(int(T))

K=0
for x in S:
    K+=(x<=N)
print(K)