"""

0,3,6,9しか使えない

"""

N = int(input())

lis = [ [0,3,6,9] ]
for i in range(8):
    new = []
    for j in lis[i]:

        if j != 0:
            new.append(j * 10 + 0)
            new.append(j * 10 + 3)
            new.append(j * 10 + 6)
            new.append(j * 10 + 9)
    lis.append(new)

#print (max(lis[-1]))

new = []
for i in range(1,10):
    for j in range(10):
        if (i+j) % 3 == 0:
            new.append(i*10+j)
lis.append(new)



ans = 0
#print (lis[2])
for i in range(len(lis)):
    if i <= 1:
        continue
    for j in lis[i]:
        if 10 < j <= N:
            ans += 1
print (ans)