#include<bits/stdc++.h>
using namespace std;

int main()
{
	int N;
	cin>>N;
	
	int freq[105]={0},a[105];
	
	int i;
	for (i=0;i<N;i++)
	{
		cin>>a[i];
		freq[a[i]]++;
	}
	
	int maxi=0;
	for (i=0;i<=100;i++)
	{
		maxi=max(maxi,freq[i]+freq[i+1]);
	}
	
	
	cout<<maxi;
}