#include<bits/stdc++.h>
#include<vector>
#include<set>
#include<stack>
#include<queue>
#include<list>
#include<map>
#define ll long long
#define INF 2000000000
#define NINF -2000000000
#define MOD 1000000007
#define br '\n'
using namespace std;
int main()
{
	ios_base::sync_with_stdio(false);
	cin.tie(0);
	//freopen("input.txt","r",stdin);
	//freopen("output.txt","w",stdout);
	int n;
	cin>>n;
	int a[101]={0};
	int x;
	for(int i=0;i<n;i++)
	{
		cin>>x;
		a[x]++;
	}
	int ans=0;
	for(int i=1;i<=100;i++)
	{
		ans=max(ans,a[i]+a[i-1]);
	}
	cout<<ans<<br;
	return 0;
}