import copy

N = int(input())
sushi = list(map(int,input().split()))
sushi_sorte = copy.copy(sushi)
num = [i for i in range(N)]
check = [0 for j in range(N)]

for i in range(N):
    for j in range(N):
        if sushi_sorte[i] > sushi_sorte[j]:
            tmp1 = sushi_sorte[i]
            tmp2 = num[i]
            sushi_sorte[i] = sushi_sorte[j]
            num[i] = num[j]
            sushi_sorte[j] = tmp1
            num[j] = tmp2

ans = 0
length = len(sushi_sorte) - 1

for i in range(N):
    if i != 0:
        if num[i] == 0:
            if check[1] != 1:
                check[0] = 1
                ans += sushi_sorte[i]
        elif num[i] == length:
            if check[length - 1] != 1:
                check[length] = 1
                ans += sushi_sorte[i]
        else:
            if check[num[i] - 1] != 1 and check [num[i] + 1] != 1:
                check[num[i]] = 1
                ans += sushi_sorte[i]
    else:
        ans += sushi_sorte[i]
        check[num[i]] = 1


print(ans)