n=int(input())
a=list(map(int,input().split()))
print(a)
c=s=2
if n<2:
 print(1)
else:
 for i in range(n-2):
  s=s+1 if a[i+2]+a[i]==2*a[i+1]else 2
  c=max(c,s)
 print(c)