s=[int(i) for i in input()]
n=reduce(lambda a,b:a+b,s)
if s.count(s[0])==len(s):
    print(str(s[0])*len(s))
elif n%36==0:
    print(36)
elif n%9==0:
    print(9)
elif n%3==0:
    print(3)
else:
    print(1)