#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;
#define N 200

int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    int n,arr[N];
    vector<int> number, count;
    
    cin>>n;
    
    for(int i=0; i<n; i++){
        cin>>arr[i];
    }
    
    sort(arr, arr+n);
    int prev=0;
    for(int i=0; i<n; i++){
        if(arr[i]!=prev){
            number.push_back(arr[i]);
            count.push_back(1);
            prev = arr[i];
        }else{
            count[count.size()-1]++;
        }
    }
    int mx=0;
    for(int i=0; i<number.size(); i++){
        int the_val;
        if(i>0 && (number[i]-number[i-1])==1){
            the_val = count[i]+count[i-1];
        }else{
            the_val = count[i];
        }
        
        if(mx<the_val){
            mx=the_val;
        }
    }
    
    cout<<mx<<endl;
    
    return 0;
}