def get_digit_list(x):
    digits, d = [], 1
    for _ in range(len(str(x))):
        digits.append(x % (d * 10) // d)
        d *= 10
    digits.reverse()
    return digits

def is_palindrom(x):
    digits = get_digit_list(x)
    digits_reversed = digits.copy()
    digits_reversed.reverse()
    for i in range(len(digits)):
        if digits[i] != digits_reversed[i]:
            return False
    return True

def palindrom_count(x):
    count = 0
    for i in range(1, x + 1):
        if is_palindrom(i):
            count += 1
    return count

def process():
    x = int(input())
    print(palindrom_count(x))

if __name__ == "__main__":
    process()