import sys
input = sys.stdin.readline
def MI(): return map(int, input().split())

a, b, c = MI()

if a == b == c:
    print(a)
elif a != b and b != c and c != a:
    tmp = [a, b, c]
    for i in range(4):
        if i in tmp:
            continue
        else:
            print(i)
else:
    if a == b:
        print(c)
    elif b == c:
        print(a)
    else:
        print(b)