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


int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */  
    int n;
    cin>>n;
    vector<int> vec;
    for(int i=0;i<n;i++)
        {
        int t;
        cin>>t;
        vec.push_back(t);
    }
    sort(vec.begin(),vec.end());
    unordered_set<int> uset;
    vector<int> unique;
    for(int i=0;i<vec.size();i++)
        {
        if(uset.find(vec[i])==uset.end())
            {
            uset.insert(vec[i]);
            unique.push_back(vec[i]);
        }
    }
    vector<int> coun;
    for(int i=0;i<unique.size();i++)
        {
        int count=0;
        for(int j=0;j<vec.size();j++)
            {
            if(vec[j]==unique[i])
                {
                count++;
            }
        }
        coun.push_back(count);
    }
    int maxcount=0;
    int count=0;
    for(int i=0;i<unique.size()-1;i++)
        {
        count=0;
        if(abs(unique[i]-unique[i+1])<=1)
            {
            count=coun[i]+coun[i+1];
        }
        maxcount=max(maxcount,count);
    }
    for(int i=0;i<coun.size();i++)
        {
        maxcount=max(maxcount,coun[i]);
    }
    
    cout<<maxcount;
    return 0;
}