n = input().strip()

# Check if all digits are the same
all_same = True
first = n[0]
for c in n:
    if c != first:
        all_same = False
        break

if all_same:
    print(n)
else:
    s = sum(int(c) for c in n)
    if s % 9 == 0:
        print(s)
    else:
        import math
        g = math.gcd(s, 9)
        print(g)