n=int(input())
a=list(map(int,input().split()))
s=[a[i+1]-a[i]for i in range(n-1)]
l=1
for i in range(n*n):
 x=i//n
 y=i%n
 if y>x:
  if len(set(s[x:y]))<2:
   l=max(l,y-x+1)
print(l)