Prime Ring Problem

#include <bits/stdc++.h>
using namespace std;
#define ll long long
ll pp[100];
bool used[100],xx[100];
ll n;

bool prime(ll cc)
{
    for(ll i=2;i*i<=cc;i++)
    {
        if(cc%i==0)
        {
            return 0;
        }
    }
    return 1;
}

void primetrack(ll ind)
{

    if(ind==n && xx[pp[n-1]+pp[0]])
    {
        cout<<pp[0];
        for(ll j=1;j<n;j++)
        {
            cout<<" "<<pp[j];
        }

        cout<<endl;
        return;

    }

    for(ll i=2;i<=n;i++)
    {
        if(used[i]==0 && xx[pp[ind-1]+i])
        {
            used[i]=1;
            pp[ind]=i;
            primetrack(ind+1);
            used[i]=0;
        }
    }

    return;
}

int main()
{
   ios_base::sync_with_stdio(0);
   cin.tie(0);cout.tie(0);

   for(ll h=2;h<=40;h++)
   {
       xx[h]=prime(h);
   }

   pp[0]=1;
   ll x=1;
   while(cin>>n)
   {
       if(x>1) cout<<endl;
       cout<<"Case "<<x<<":"<<endl;
       x++;
       primetrack(1);
   }


   return 0;
}