1015. Reversible Primes

A reversible prime in any number system is a prime whose "reverse" in that number system is also a prime. For example in the decimal system 73 is a reversible prime because its reverse 37 is also a prime.

Now given any two positive integers N (< 10⁵) and D (1 < D <= 10), you are supposed to tell if N is a reversible prime with radix D.

Input Specification:

The input file consists of several test cases. Each case occupies a line which contains two integers N and D. The input is finished by a negative N.

Output Specification:

For each test case, print in one line "Yes" if N is a reversible prime with radix D, or "No" if not.

Sample Input:

73 1023 223 10-2

Sample Output:

Yes
Yes

No

#include <cstdio>

#include <cstdlib>

#include<iostream>

using namespace std;

#include <deque>

#include <queue>

#include <string>

#include <vector>

#include <iomanip>

#include<algorithm>

#include<math.h>

using namespace std;

#define max1 600

#define inf 1000

bool isprime(int a)

{

    int i;

    if(a==1)

        return false;

    if(a==2)

        return true;

    for(i=2;i<=sqrt(a);i++)

    {

        if(a%i==0)

            return false;

    }

    return true;

}

int truen(int n,int d)

{

    int sum=0;

    while(n)

    {

        sum=sum*d+n%d;

        n/=d;

    }

    return sum;

}

int main()

{

  int N,M,s;

  while(1)

  {

      cin>>N;

      cin>>M;

      if(N<0)

        break;

      s=truen(N,M);

      if(isprime(N)&&isprime(s))

        cout<<"Yes"<<endl;

    else

        cout<<"No"<<endl;

  }

  return 0;

}