#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 arr_count[102];
    
    for(int i=1; i<=100; i++)
        arr_count[i] = 0;
    
    for(int i=0; i<n; i++)
        arr_count[a[i]]++;
    
    int county = 0;
    for(int i=1; i<100; i++){
        if(arr_count[i] != 0 && arr_count[i+1] != 0){
            if(arr_count[i] + arr_count[i+1] > county)
                county = arr_count[i] + arr_count[i+1];
        }
    }
    
    for(int i=1; i<100; i++){
        if(arr_count[i] > county)
            county = arr_count[i];
    }
    
    cout << county << endl;
    return 0;
}