n = int(input())
a = input()
if ' ' in a:
    print('assert')
else:
    a = int(a)
    b = int(input())
    c = int(input())
    l = list(set(sorted([a+b, b+c, c+a])))
    if len(l)==2:
        print(l[0])
    else:
        print(l[1])