a, b, c = map(int, input().split())
if a==b and b==c:
    d = a
elif a!=b and a!=c and b!=c:
    d = 6 - (a+b+c)
else:
    if a==b:
        d = c
    elif a==c:
        d = b
    else:
        d = a
print(d)