#include<iostream>
#include<algorithm>
using namespace std;
#define ll long long int

int main()
{
    ll n;
    cin>>n;
    ll ar[105];
    for(ll i=0;i<105;i++) ar[i]=0;
    
    ll item;
    for(ll i=0;i<n;i++)
    {
        cin>>item;
        ar[item]++;
    }
    ll max=0;
    for(ll i=0;i<104;i++)
    if(max<ar[i]+ar[i+1])
    max=ar[i]+ar[i+1];
    
    cout<<max;
    return 0;
}