a = []
n = int(input())
for i in range(0,7):
    a.append(int(input()))
ms = 0
maxs = 0
for i in range(1,n-7):
    a[8] = int(input())
    if a[1]>ms:
        ms=a[1]
    if ms+a[8] > maxs:
        maxs = ms+a[8]
    for j in range(1,7):
        a[j] = a[j+1]
print(maxs)