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


int main() {
    int n;
    std::cin >> n;
    std::vector<int> numbers;
    
    int a;
    for (int i = 0; i < n; ++i)
    {
        std::cin >> a;
        numbers.push_back(a);
    }
    
    std::sort(numbers.begin(), numbers.end());
    
    int cur_count = 0;
    int max_count = 0;
    int j;
    for (int i = 0; i < numbers.size(); ++i)
    {
        j = i + 1;
        cur_count = 1;
        while (j < numbers.size())
        {
            if (numbers[j] < numbers[i] + 2)
            {
                ++j;
                ++cur_count;
            }
            else break;
        }
        if (cur_count > max_count) max_count = cur_count;
    }
    
    std::cout << max_count;
    
    return 0;
}