#!/bin/python3

import sys

def solve(aa):
    cache = [0] * 101
    for a in aa:
        cache[a] += 1
    mx = 0
    for i in range(1, len(cache)):
        v = cache[i - 1] + cache[i]
        if v > mx:
            mx = v
    return mx

n = int(input().strip())
a = [int(a_temp) for a_temp in input().strip().split(' ')]
print(solve(a))