import sys
input = sys.stdin.readline
N = int(input())
a = list(map(int, input().split()))
res = 0
table = [0] * (N + 1)
for i in range(N): table[a[i]] = i + 1

sm = 0
for i in range(N):
  sm += table[i]
  res = max(res, sm - table[i + 1])
print(res)