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

freq = {}
for x in (a, b, c):
    freq[x] = freq.get(x, 0) + 1

if len(freq) == 1:
    print(a)
else:
    max_count = max(freq.values())
    if max_count == 2:
        # Find the element with count 1
        for key, count in freq.items():
            if count == 1:
                print(key)
                break
    else:
        # All three are different, find missing one
        for i in range(4):
            if i not in freq:
                print(i)
                break