#include <bits/stdc++.h>

using namespace std;

int main(void){
	int n;
	cin >> n;
	int a[n];
	for(int i = 0; i < n;i += 1)cin >> a[i];
	sort(a, a+n);
	int ans = 0;
	for(int i = 0; i < n; i += 1){
		for(int j = i+1; j < n; j += 1){
			if (a[j]-a[i] <= 1)
				ans = max(ans, j-i+1);
		}
	}
	cout << ans << endl;
}