def solve():
    n = int(input())
    a = input()
    if " " in a:
        return "assert"
    a = int(a)
    b = int(input())
    c = int(input())
    ans = sorted([a + b, a + c, b + c])[::-1]
    return ans[1] if ans[0] != ans[1] else ans[2]
print(solve())