n = int(input())//(10**9+1)
from itertools import product
x1 = [1,101,10001,1000001,100000001]
x2 = [11,1001,100001,10000001]
ans = 0
for d in range(1,10,2):
    c = repeat=(d+1)//2
    for a in product(range(10),repeat=c):
        v = sum(xi*ai for xi,ai in zip(x1,a))
        if 0 < v <= n and v%10: ans += 1
    for i in range(c):
        x1[i] *= 10
for d in range(2,10,2):
    c = d//2
    for a in product(range(10),repeat=c):
        v = sum(xi*ai for xi,ai in zip(x2,a))
        if 0 < v <= n and v%10: ans += 1
    for i in range(c):
        x2[i] *= 10
print(ans)