#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;
    cin >> n;
    vector<int> a(n);
    vector<int> b(n+1);
    for(int i=0;i<n+1;i++)
        b[i]=0;
    
    for(int a_i = 0;a_i < n;a_i++){
       cin >> a[a_i];
        b[a[a_i]]++;
    }
    
   // for(int i=0;i<n+1;i++)
     //   cout<<b[i]<<" ";
    //cout<<endl;
    
    int max;
    if(a[0]>0)
        max=b[a[0]]+(b[a[0]+1]>b[a[0]-1]?b[a[0]+1]:b[a[0]-1]);
    else
        max=b[a[0]]+b[a[0]+1];
    
   // cout<<max<<endl;
    
    for(int i=1;i<n;i++){
        if(a[i]>0 && b[a[i]]+(b[a[i]+1]>b[a[i]-1]?b[a[i]+1]:b[a[i]-1])>max)
            max=b[a[i]]+(b[a[i]+1]>b[a[i]-1]?b[a[i]+1]:b[a[i]-1]);
        else if(b[a[i]]+b[a[i]+1]>max)
             max=b[a[i]]+b[a[i]+1];
    }
    cout<<max<<endl;
    return 0;
}