#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];
    }
    int count[101];
    memset(count, 0, sizeof count);        
    for (int i = 0;i < n;++i) {
        count[a[i]] ++;
    }
    int res = count[1] + count[2];
    for (int i = 2; i < 99; ++i) 
        res = max(res, count[i] + count[i+1]);
    cout<<res<<endl;
    return 0;
}