#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);
    for(int a_i = 0;a_i < n;a_i++){
       cin >> a[a_i];
    }
    
    sort(a.begin(), a.end());
    
    int last = a[0];
    int count =1;
    int maxCount = 0;
    for(int i = 1;i < n;i++){
        if(a[i] - last <= 1){
            count++;
            if(count > maxCount)
                maxCount = count;
        }else{
            last = a[i];
            count = 1;
        }
    }
    cout << maxCount << endl;
    return 0;
}