n = int(input().strip())
a = [int(a_temp) for a_temp in input().strip().split(' ')]
a=list(sorted(a))
list1=[]
count=0
#print(a)
for i in range(n):
    count=0
    for j in range(i,n):
        if(abs(a[i]-a[j])<=1):
            count+=1
        else:
            break
    list1.append((count))        
#print(list1)
print(max(list1))