#include <bits/stdc++.h>
using namespace std;
#define fr first
#define sc second
#define sz(c) int(c.size())
#define all(c) c.begin(), c.end()
#define rall(c) c.rbegin(), c.rend()

int a[1007];
int n;
int main() {
	cin >> n;
	int mx = -1;
	int a[107];
	for (int i = 0; i < n; ++i) {
		scanf("%d",&a[i]);
	}
	sort(a , a + n);
	for (int i = 0; i < n;i++) {
		for (int j = i+1; j < n; ++j) {
			if(a[j] - a[i] <= 1)
				mx = max(mx , j - i + 1);
		}
	}
	cout << mx << endl;

}