n = int(input())

if n <= 10**9:
    print(0)

if n >= 10**18 - 1:
    print(109998)

else:
    
    a = []
    
    for i in range(5):
        a_i = []
        for j in range(10**i, 10**(i + 1)):
            a_i.append(j)
            if i == 0:
                a.append(j)
            else:
                a.append(j * 10**i + int(str(j)[:i][::-1]))
        if i <= 3:
            for j in a_i:
                a.append(j * 10**(i + 1) + int(str(j)[::-1]))
    
    a.sort()
    m = n // 10**9
    k = 0
    while m > a[k]:
        k += 1
    if n < a[k] * 10**9 + a[k]:
        print(k)
    else:
        print(k + 1)