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


int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    int n;
    cin>>n;
    
    vector<int> v(n);
    
    for(int i=0; i<n; i++)
        cin>>v[i];
    
    sort(v.begin(),v.end());
    int max = 0;
   
    int cur = v[0];
    int ct = 1;
    for(int i=1; i<n; i++){
       if(v[i] - cur <= 1)
           ct++;
       
        else{
            if(ct>max)
                max = ct;
            ct = 1;
            cur = v[i];
        }
    }
    
    if(ct > max)
        max = ct;
    
    cout<<max<<endl;
    return 0;
}