#include <cstdio>
#include <iostream>
#include <vector>
#include <algorithm>
#include <bitset>
#include <functional>
#include <iterator>
#include <map>
#include <numeric>
#include <cstring>
#include <string>
#include <sstream>
#include <set>
#include <stack>
#include <queue>
#include <cctype>
#include <math.h>
#include <cstdlib>

using namespace std;

#define I64 long long int
#define INF 0x7f7f7f7f

#define PII pair <int, int>
#define PLL pair <I64, I64>
#define PDD pair <double, double>
#define PSI pair <string, int>
#define PIS pair <int, string>
#define PSS pair <string, string>

#define MII map <int, int>
#define MLL map <I64, I64>
#define MDD map <double, double>
#define MSI map <string, int>
#define MIS map <int, string>
#define MSS map <string, string>

#define VI vector <int>
#define VS vector <string>
#define QI queue <int>
#define QS queue <string>
#define SI stack <int>
#define SS stack <string>

#define pb push_back
#define pob pop_back
#define mp make_pair

#define IT iterator
#define ff first
#define ss second

#define SET(a, b) memset( a, b, sizeof (a) )
#define READ(f) freopen(f, "r", stdin)
#define WRITE(f) freopen(f, "w", stdout)

#define IAMHERE cout << "YES\n";
#define DEBUG(a, b) cout << a << ": " << b << "\n";

#define SIZE 1000
#define MAX 2000
#define EPS 1e-9
#define PI 2*acos(0.0)

int a[MAX];

int main()
{
    //READ("in.txt");
    //WRITE("out.txt");
    int Case=1;
    int n, m, k;
    char dump[2];

    //int tc; scanf("%d", &tc);

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

    	sort(a, a + n);
    	vector <int> v;
    	int ans = 0;

    	for (int i = 0; i < n; i++) {
    		v.push_back(a[i]);
    		for (int j = i + 1; j < n; j++) {
    			bool flag = true;
    			for (int k = 0; flag && k < v.size(); k++) {
    				if (abs(a[j] - v[k]) > 1) {
    					flag = false;
    				}
    			}
    			if (flag) v.push_back(a[j]);
    		}
    		ans = max(ans, (int)(v.size()));
    		v.clear();
    	}
    	cout << ans << "\n";
    }
    return 0;
}