#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>
#include <set>


using namespace std;


int main(){
    int n;
    cin >> n;
    vector<int> a(n);
    map<int,int> m;
    set<int> s;
    int count=0;
    int index=-1;
    for(int i = 0;i < n;i++){
       cin >> a[i];
       m[a[i]]++;
        if(m[a[i]]+m[a[i]-1]>count) 
        {
            count=m[a[i]]+m[a[i]-1];
            index=i;
        }
       else if(m[a[i]]+m[a[i]+1]>count) 
       {
           count=m[a[i]]+m[a[i]+1];
           index=i;
       }
    }
    if(m[a[index]-1]>m[a[index]+1])
        count=m[a[index]-1];
    else
        count=m[a[index]+1];
    count+=m[a[index]];
    cout<<count;
    return 0;
}