#include <bits/stdc++.h>
using namespace std;
int main()
{
	ios::sync_with_stdio(0);
	int N;
	cin>>N;
	int xy[200] = {0};
	for (int i = 0; i < N; ++i)
	{
		int l;
		cin>>l;
		xy[l]++;
	}	
	int maxi = 0;
	for (int i = 0; i < 100; ++i)
	{
		maxi = max(maxi, xy[i] + xy[i+1]);
	}
	cout<<maxi<<'\n';
}