#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
//#include<stdlib>
#include<bits/stdc++.h>
using namespace std;


int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    
	int n; cin >> n;
	int a[105]; int u; memset(a,0,sizeof a);
	for (int i = 0; i < n; i++)cin >> u, a[u]++;
	int ans = -5;
	for (int i = 0; i < 100; i++)ans = max(ans, a[i] + a[i + 1]);

	cout << ans;
    return 0;
}