#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);
    vector<int> count(100);
    for(int a_i = 0;a_i < n;a_i++){
        int x;cin>>x;
       count[x]++;
    }
    vector<int> c2(100);
    for (auto i = 0; i<99; i++) {
        c2[i] = count[i]+count[i+1];
    }
    cout<<*max_element(c2.begin(), c2.end());
    return 0;
}