n = int(input())
l = list(map(int, input().split()))
S1 = []
S2 = []
for i in range(1,len(l)+1):
    s1 = i**2 + l[i-1]**2
    s2 = i**2 - l[i-1]**2
    S1.append(s1)
    S2.append(s2)
m = max(max(S1) - min(S1),max(S2) - min(S2))
print(m)