#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>
#define ll long long int
using namespace std;


int main(){
    int n;
    cin >> n;
    ll a[n];
    for(ll i=0;i<n;i++)
        {
        cin>>a[i];
    }
    ll b[100];
    memset(b,0,sizeof(b));
    for(ll i=0;i<n;i++)
        {
        b[a[i]]++;
    }
    //sort(b,b+100);
    ll temp=-100;
    for(ll i=1;i<100;i++)
        {
        temp=max(temp,b[i]+b[i-1]);
    }
    cout<<temp;
    return 0;
}