N = int(input())

As = set()
for _ in range(N):
    A = input()
    if ' ' in A:
        print('assert')
        break
    A = int(A)
    if len(As) < 3:
        As.add(A)
    else:
        for i in range(len(As)):
            if As[i] < A:
                As.insert(i, A)
                As.pop()
else:
    As = sorted(list(As), reverse=True)
    if len(As) < 2:
        print(As[len(As) - 1] * 2)
    else:
        print(As[0] + As[2])