#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 acount[ 100 ];

int main(){
    int n;
    cin >> n;
    vector<int> a(n);
    for ( int i = 0; i < 100; ++i ) {
        acount[ i ] = 0;
    }
    for(int a_i = 0;a_i < n;a_i++){
       cin >> a[a_i];
        acount[ a[ a_i ] ]++;
    }
    int max_count = 0;
    for ( int i = 1; i < 100-1; ++i ) {
        if ( acount[ i ] + acount[ i + 1 ] > max_count ) {
            max_count = acount[ i ] + acount[ i + 1];
        }
    }
    cout << max_count << endl;
    return 0;
}