#include <bits/stdc++.h>
#define TASK "magic"
#define pb push_back
#define fi first
#define se second
using namespace std;

#ifdef LOCAL
	#define eprintf(...) fprintf(stderr, __VA_ARGS__)
#else
	#define eprintf(...) (void)42
#endif

// every true-boy doesn't read statement!

typedef long long ll;
typedef vector < int > vi;
typedef pair < int, int > pii;
typedef vector < pii > vpii;

const int MAXN = (int)4e5 + 22;
const int INF = (int)1e9 + 47;
const int MAXN_LOG = 19;

int N;
int a[MAXN];

void solve() {
	cin >> N;
	for (int i = 0; i < N; i++)
		cin >> a[i];
	sort(a, a + N);
	for (int len = N; len > 0; len--) {
		for (int i = 0; i <= N - len; i++) {
			int j = i + len - 1;
			if (abs(a[i] - a[j]) <= 1) {
				cout << len;
				return;
			}
		}
	}
}

int main() {
	ios_base::sync_with_stdio(0);
	cin.tie(0);
#ifdef LOCAL
	assert(freopen("xxx.in", "r", stdin));
	assert(freopen("xxx.out", "w", stdout));
#endif
	solve();
	return 0;
}