Uva 10490 - Mr. Azad and his Son!!!

/*
    Uva 10490 - Mr. Azad and his Son!!!
    Verdict: Accepted
    Time : 0.000

    ==> Perfect Numbers problem. All perfect numbers are prime number. 2^p+1 * (2^p + 1) ; where p is a prime number. But except 11 23 and 29 till 32

*/
#include <iostream>
#include <cstdio>
#include <cstring>
#include <string>
#include <vector>
#include <cmath>
#include <cctype>
#include <sstream>
#include <set>
#include <list>
#include <stack>
#include <queue>
#include <algorithm>
#define sf scanf
#define pf printf
#define sfint scanf ("%d %d",&a,&b)
#define sfl scanf ("%ld %ld",&a,&b)
#define sfll scanf ("%lld %lld",&a,&b)
#define sfd scanf ("%lf %lf",&a,&b)
#define sff scanf ("%f %f",&a,&b)
#define LL long long
#define L long
#define N 32
#define MOD 10000000007
#define pb push_back
#define sz size()
#define gc getchar ()
#define ps push
#define clr clear
#define bn begin()
#define ed end()

using namespace std;

bool flag [N];

int prime [12],len=0;

void sieve ()
{
    for (int i=4;i<=N;i+=2)
    {
        flag[i] = true;
    }

    //v.push_back(2);
    prime[len] = 2; len++;

    for (int i=3;i<=N;i+=2)
    {
        if (!flag[i])
        {
            //v.push_back(i);
            prime[len] = i; len++;
            //return false;
        }

        for (int j=i*i;j<=N;j+=i)
        {
            flag[j] = true;
        }
    }
}

int main ()
{
    sieve();

    //for (int i=0;i<len;i++) cout << prime[i] << " ";

    LL n,k,p,t;

    while (cin >> n and n!=0)
    {
        t = n;

        if (n == 11 or n == 23 or n == 29)
        {
            cout << "Given number is prime. But, NO perfect number is available." << endl;
            continue;
        }

        if (!flag[n])
        {
            k = t-1;
            p = pow(2,k) * (pow(2,t) - 1);
            cout << "Perfect: " << p <<"!" << endl;
        }

        else
        {
            cout << "Given number is NOT prime! NO perfect number is available." << endl;
        }
    }

    return 0;
}