#include <bits/stdc++.h>

#define F first
#define S second
#define mp make_pair
#define pb push_back
#define sz(x) x.size()
#define all(x) x.begin(), x.end()
#define pii pair < int , int >

using namespace std;

typedef long long ll;
typedef long double ld;
typedef unsigned long long ull;

const int N = 1e6 + 123;
const int mod = 1e9 + 7;
const int INF = 1e9 + 1;
const ll INFL = 3e18 + 1;
const double pi = acos(-1.0);

int n, a[303];

int main () {
	
	ios_base::sync_with_stdio (0);
	cin.tie (0);
	cin >> n;
	for (int i = 1;i <= n;i ++) cin >> a[i];
	sort (a + 1, a + n + 1);
	int l = 1, r = 0, mx = 0;
	while (l <= n && r <= n) {
		if (a[r] - a[l] > 1) l ++;
		else r ++;
		mx = max (r - l + 1, mx);
	}
	cout << mx - 1;


return 0;       
}