n = int(raw_input())
a = map(int, raw_input().split())

a.sort()
ans = 1
for i in xrange(n-1):
    dp = [1]*n
    tempAns = 1
    for j in xrange(i+1, n):
        if abs(a[j]-a[i])<=1:
            tempAns+=1
    ans = max(tempAns, ans)
print ans