#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 a[200], answer, x;
int main(){
    int n;
    cin >> n;
    for(int a_i = 0;a_i < n;a_i++){
       cin >> x;
       a[x] ++;
    }
    
    for(int i = 0; i < 100; ++ i)
    {
        answer = max(answer, a[i]);
    }
    
    for(int i = 1; i < 100; ++ i)
    {
        answer = max(answer, a[i] + a[i - 1]);
    }
    cout << answer;
    return 0;
}