#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 cnt[101];
int main(){
    
    int n, a;
    cin >> n;
    for(int i = 0; i < n; i++)
    {
        cin>>a;
        cnt[a]++;
    }
    int mx = 0, sum = 0;
    for(int i = 0; i < 100; i++){
        sum = cnt[i] + cnt[i+1];
        if(sum > mx)
            mx = sum;
    }
    cout<<mx;
    return 0;
}