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


int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    int n;
    cin>>n;
    int a[n],c=0,max=-1,k;
    map<int ,int> p;
    for(int i=0;i<n;i++)
    {cin>>k;p[k]++;}
    map<int ,int>::iterator pp=p.begin(),ppp=p.begin();
    ppp++;
    while(pp!=p.end())
        {
        if(abs(pp->first-ppp->first)<=1)
        {c=pp->second+ppp->second;}
        if(c>max)
            max=c;
        if(pp->second>max)
            max=pp->second;
        pp++;ppp++;
        }
    if(abs(pp->first-ppp->first)<=1)
        {c=pp->second+ppp->second;}
        if(c>max)
            max=c;
        if(pp->second>max)
            max=pp->second;
   
    cout<<max;
    return 0;
}