#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 maksi = 0,broj = 0;
    int i = 0;
    while(i < n-1){
        broj = 1;
        int j = i;
        while(i < n-1 && a[j] >= a[i+1]-1){
            i++;
            broj++;
        }
        if(broj > maksi){
            maksi = broj;
        }
        i++;
        //cout << maksi << endl;
    }
    
    cout << maksi << endl;
    return 0;
}