#include <map>
#include <set>
#include <list>
#include <cmath>
#include <ctime>
#include <deque>
#include <queue>
#include <stack>
#include <string>
#include <bitset>
#include <cstdio>
#include <limits>
#include <vector>
#include <climits>
#include <cstring>
#include <cstdlib>
#include <fstream>
#include <numeric>
#include <sstream>
#include <iostream>
#include <algorithm>
#include <unordered_map>

using namespace std;


int main() {
	int n;
	cin >> n;
	vector<int> a(n);
	for (int a_i = 0; a_i < n; a_i++) {
		cin >> a[a_i];
	}

	vector<int> dict(100, 0);

	for (auto num : a) {
		++dict[num];
	}

	int result = 0;

	for (size_t i = 1; i < dict.size(); ++i) {
		result = std::max(result, (dict[i] + dict[i - 1]));
	}

	cout << result;

	return 0;
}