N = int(input())
M = 10**9+1

S = set()
ans = 0
for j in range(1,10):
    if j*M <= N:
        ans += 1

for i in range(1, 10**4):
    si = str(i)
    rev = si[::-1]
    if int(si+rev)*M <= N:
        ans += 1
    for j in range(10):
        if int(si+str(j)+rev)*M <= N:
            ans += 1

print(ans)