N = int(input())
ten = 10 ** 9
if N < ten + 1:
    print(0)
    exit()

a, b = N // ten, N % ten
if a > b:
    a -= 1

ans = 0
M = 10**5 + 5
for i in range(1, M):
    s = str(i)
    n = int(s + s[::-1])
    
    if n <= a:
        ans += 1
    else:
        break

for m in range(10):
    for i in range(M):
        if i == 0:
            s = ""
        else:
            s = str(i)
        n = int(s + str(m) + s[::-1])
        if n <= a:
            ans += 1
        else:
            break

print(ans - 1)