#include<bits/stdc++.h>
using namespace std;

#define ll long long
int main()
{
    ll int n; cin>>n;
    ll i;
    ll b[100]={0};
    for(i=0;i<n;i++)
    {
        ll x;
        cin>>x;
        b[x]++;
    }

    ll maxv=0;
    //for(i=1;i<=99;i++)
        //cout<<i<<" "<<b[i]<<endl;
    for(i=1;i<99;i++)
    {
        ll ans=0;
            ans = b[i]+b[i+1];
            //cout<<ans<<endl;
        if(ans>=maxv) maxv = ans;
    }
    cout<<maxv<<endl;






}