import sys
input = sys.stdin.readline

a,b,c=map(int,input().split())

if a==b==c:
    print(a)
    exit()

if a==b:
    print(c)
    exit()
if b==c:
    print(a)
    exit()
if a==c:
    print(b)
    exit()


print(6-a-b-c)