import sys
input = lambda :sys.stdin.readline()[:-1]
ni = lambda :int(input())
na = lambda :list(map(int,input().split()))
sys.setrecursionlimit(10**7)
yes = lambda :print("yes");Yes = lambda :print("Yes");YES = lambda : print("YES")
no = lambda :print("no");No = lambda :print("No");NO = lambda : print("NO")
#######################################################################
n = ni()
p = na()
a = [-1]*n
for i in range(n):
    a[p[i]-1] = i+1
ans = 0
for i in range(n):
    ans = max(ans, (n-i)*(n+1-i)//2-2*a[-1-i])
print(ans)