#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,count,maxc=2;
    cin >> n;
    int a[n];
    for(int i=0;i<n;i++)
        cin>>a[i];
    for(int i=0;i<=100;i++)
        {
        count=0;
        for(int j=0;j<n;j++)
            if(((i-a[j])==1)||(a[j]==i))
            count++;
           // cout<<count<<" ";
            if(count>maxc)
            maxc=count;
    }
    //cout<<endl;
    cout<<maxc;
    return 0;
}