#include <bits/stdc++.h>

using namespace std;

#define ll long long
#define pb push_back
#define mp make_pair
#define F first
#define S second
#define make0(a) memset(a,0,sizeof(a))
#define make1(a) memset(a,-1,sizeof(a))
#define all(v) v.begin(),v.end()
#define sc(i) scanf("%d",&i)
#define pi pair <int,int>

const int mod = 1e9+7;

int max(int a,int b,int c) { return max(max(a,b),c); }

int min(int a,int b,int c) { return min(min(a,b),c); }

void input(int a[],int n) { for (int i = 0; i < n; ++i) { scanf("%d",&a[i]); } }

int main()
{
	int n,a;
	cin >> n;
	int arr[n];
	input(arr,n);
	int hash[1000];
	make0(hash);
	for (int i = 0; i < n; ++i)
	{
		hash[arr[i]] ++;
	}
	int mx = 0;
	for (int i = 0; i < 500; ++i)
	{
		mx = max(mx,hash[i]+hash[i+1]);
	}
	cout << mx << endl;
	return 0;
}