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


int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */ 
    int ma=0;
    int n,i,j,k;
    cin>>n;
map<int,int>m;
    set<int>s;
    int a[n];
    for(i=0;i<n;i++)
        {
        cin>>a[i];
        m[a[i]]+=1;
        s.insert(a[i]);
    }
   set<int>::iterator it;
    for(it=s.begin();it!=s.end();it++)
        {
        int p=*it;
        int p1=m[p];
        int p2=max(m[p-1],m[p+1]);
        ma=max(ma,p2+p1);
    }
    cout<<ma;
}