#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 freq[100];

int main(){
    int n;
    cin >> n;
    vector<int> a(n);
    for(int a_i = 0;a_i < n;a_i++){
       cin >> a[a_i];
    }
    
    memset(freq, 0, sizeof(freq));
    for (int a_i : a) {
        freq[a_i]++;
    }
    
    int ret = 0;
    for (int i = 1; i < n; ++i) {
        int sum = freq[i - 1] + freq[i];
        ret = max(sum, ret);
    }
    
    cout << ret << endl;
    return 0;
}