#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


int main() {
    int n;
	cin >> n;
	vector<int> lis(n, 0), tab(n);
	for (int i = 0; i<n; i++) {
		cin >> tab[i];
	}
	sort(tab.begin(), tab.end());
	
	int max = -1;
	for (int i = n - 1; i >= 0; i--) {
		int count = 1;
		for (int j = i - 1; j >= 0; j--) {
			if (abs(tab[i] - tab[j]) <= 1)
				count++;
		}
		if (max < count)
			max = count;
	}
	cout << max << endl;
    return 0;
}