n = int(input())
arr = [int(x) for x in input().split(" ")]

arr = sorted(arr)
maxc = 0
maxmax = 1

max_limit = 0
min_limit = 0

for i, x in enumerate(arr):
    if i == 0:
        maxc += 1
        max_limit = x
        min_limit = x
        continue
    if abs(x - max_limit) <= 1 and abs(x - min_limit) <= 1:
        maxc += 1
        max_limit = max(x, max_limit)
        min_limit = min(x, min_limit)

        if maxc > maxmax:
            maxmax = maxc
    else:
        maxc = 1
        max_limit = x
        min_limit = x

print(maxmax)