#!/bin/python3

import sys


n = int(input().strip())
a = [int(a_temp) for a_temp in input().strip().split(' ')]
a = sorted(a)
max_l = 0
for i in range(len(a)):
    for j in range(i+1, len(a)):
        if a[j] - a[i] <= 1:
            if j != len(a)-1:
                continue
            else:
                max_l = max(max_l, j-i+1)
                break
        else:
            max_l = max(max_l, j-i)
            break

print(max_l)