#include <iostream>
#include <vector>
#include <unordered_map>
using namespace std;

int diff1(vector<int> a)
{
    int max = 0;
    int count = 0;
    
    int size = a.size();
    unordered_map<int, int> m;
    unordered_map<int, int>::iterator it;
    for (int i = 0; i < size; i++)
    {
        it = m.find(a[i]);
        if (it == m.end())
            m[a[i]] = 1;
        else
            m[a[i]] += 1;
    }
    
    for (int i = 0; i < size; i++)
    {
        int num = a[i];
        it = m.find(num);
        count += it->second;
        
        it = m.find(a[i] - 1);
        int temp = 0;
        if (it != m.end())
        {
            count += it->second;
            temp = it->second;
        }
        if (count > max)
            max = count;
        
        count -= temp;
        it = m.find(a[i] + 1);
        if (it != m.end())
            count += it->second;
        if (count > max)
            max = count;
        count = 0;
    }
    return max;
}

int main()
{
    int n;
    cin >> n;
    vector<int> a(n);
    for (int a_i = 0; a_i < n; a_i++)
        cin >> a[a_i];
    cout << diff1(a) << "\n";
    return 0;
}