import sys,random

input = lambda :sys.stdin.readline().rstrip()
mi = lambda :map(int,input().split())
li = lambda :list(mi())

N = int(input())
P = li()

pos = [-1 for i in range(N)]
for i in range(N):
    pos[P[i]-1] = i+1


res = 0
S = pos[0]
for i in range(1,N):
    tmp = S  - (pos[i])
    res = max(res,tmp)
    S += pos[i]
    

print(res)