cRoocked

import math

input_numbers = input()
user_list = [int(a)for a in input_numbers if a.isdigit()]

total = 0
while total < 9:

    for i in range(len(user_list)):
        user_list[i] = int(user_list[i])
        total += user_list[i]
    if total < 9:

        print(total)
        break
else:
    total= math.trunc(total)
    total = sum(map(int, str(total)))

    print(total)