n=int(input())
a=[int(num) for num in input().split()]
m=0
c=0
for i in range(n):
    p=a.count(a[i])
    q=a.count(a[i]+1)
    r=a.count(a[i]-1)
    ma=max(p+q,p+r)
    m=max(m,ma)
    
print(m)