l = list(map(int,input().split()))

l.sort()
s = set(l)
import sys
if len(s) == 1:
    print(l[0])
elif len(s) == 3:
    print(6 - sum(l))
else:
    if l[0] == l[1]:
        print(l[2])
    else:
        print(l[0])