#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */  
    int n;
	cin>>n;
	int arr[n];
	int ct[110];
	for(int i=0;i<110;i++)
		ct[i]=0;

	for(int i=0;i<n;i++)
	{
		cin>>arr[i];
		ct[arr[i]]++;
	}
	int max_p =0;
	for(int i=1;i<110;i++)
	{
		if(ct[i] + ct[i-1] > max_p)
			max_p = ct[i] + ct[i-1];

	}
	cout<<max_p<<endl;
    return 0;
}