/* ta yag odo batorshihiin code harj bn */

#include <map>
#include <set>
#include <list>
#include <cmath>
#include <ctime>
#include <deque>
#include <queue>
#include <stack>
#include <string>
#include <bitset>
#include <cstdio>
#include <limits>
#include <vector>
#include <climits>
#include <cstring>
#include <cstdlib>
#include <fstream>
#include <numeric>
#include <sstream>
#include <iostream>
#include <algorithm>

using namespace std;

typedef long long ll;

const ll MOD = 1000000009ll;
const ll INFl = 9223372036854775807ll;
const int inf = (1 << 30) - 1;

#define ff first
#define ss second
#define pb push_back
#define _N 100005
#define mk make_pair

ll power(ll x, ll y, ll z) { ll t = 1; while (y > 0) { if (y % 2) { t = (t * x) % z; } x = (x * x) % z; y /= 2; } return t; }

int movex[4] = {0, 1, -1, 0};
int movey[4] = {1, 0, 0, -1};

int a[_N];

int n, l, i;

int main () {
//	freopen ("std.in", "r", stdin);
	int n;
	scanf ("%d", &n);
	for (i = 0;i < n; i ++) {
		scanf ("%d", &l);
		a[l] ++;
	}
	int ans = 0;
	for (i = 1;i <= 101; i ++)
	ans = max (ans, a[i] + a[i - 1]);
	printf ("%d", ans);
	return 0;
}