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


int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */  
    size_t T;
    std::cin >> T;
    std::map<int, size_t> counts;
    for(size_t t{0}; t<T; ++t)
    {
        int x;
        std::cin >> x;
        ++counts[x];
    }
    if (counts.size()<2)
    {
        std::cout << counts.begin()->second << std::endl;
    }
    else
    {
        size_t maxCount{counts.begin()->second};
        for(auto itr=counts.begin(), itr2=std::next(itr); itr2!=counts.end(); ++itr, ++itr2)
        {
            if (itr2->second>maxCount) maxCount=itr2->second;
            
            if ((itr2->first)-(itr->first) == 1)
            {
                size_t count{itr2->second+itr->second};
                if (count>maxCount) maxCount=count;
            }
        }
        std::cout << maxCount << std::endl;
    }
    
    return 0;
}