#include <map>
#include <set>
#include <list>
#include <cmath>
#include <ctime>
#include <deque>
#include <queue>
#include <stack>
#include <string>
#include <bitset>
#include <cstdio>
#include <limits>
#include <vector>
#include <climits>
#include <cstring>
#include <cstdlib>
#include <fstream>
#include <numeric>
#include <sstream>
#include <iostream>
#include <algorithm>
#include <unordered_map>

using namespace std;


int main(){
    int n,count1,count2,ans=0;
    cin >> n;
    vector<int> a(n);
    vector<int> b(n);
    for(int a_i = 0;a_i < n;a_i++){
       cin >> a[a_i];
    }
    for(int i=0;i<n-1;i++)
       {
        count1=count2=0;
        for(int j=i;j<n;j++)
        if((a[i]-a[j])==1 || a[i]==a[j])
           count1++;
            
         for(int j=i;j<n;j++)
        if((a[j]-a[i])==1 || a[i]==a[j])
           count2++;   
           if(count1>ans)
            ans=count1;
           if(count2>ans)
            ans=count2;
           }
    cout<<ans;
    return 0;
}