N = int(input())
P = [0]+list(map(int,input().split()))
ans = -10**9
A = [0]*(N+1)
cnt = 0
for i in range(1,N+1):
    if P[i]<N:
        A[P[i]+1] = i
        cnt += i
    else:
        A[1] = i
        cnt -= i
ans = max(ans,cnt)
for n in range(N,1,-1):
    indn = A[n]
    ind1 = A[1]
    cnt += ind1-2*indn
    A[n],A[1] = ind1,indn
    ans = max(ans,cnt)
print(max(ans,0))