A1015 Reversible Primes (20 分)

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

bool isPrime(int n){
  if(n <= 1){
    return false;
  }
  int sqr = (int)sqrt(1.0*n);
  for(int i = 2; i <= sqr; i++){
    if(n % i == 0){
      return false;
    }
  }
  return true;
} 

int num[111];

int main(int argc, char** argv) {
  int a, d;  
  
  while(1){
    cin >> a;
    if(a < 0) break;
    cin >> d;
    
    if(isPrime(a) == false){
      cout << "No" << endl;
    } else {
      int len = 0;
      do{
        num[len++] = a % d;
        a = a / d;
      }while(a);
      for(int i = 0; i < len; i++){
        a = a * d + num[i];
      }
      if(isPrime(a) == true){
        cout << "Yes" << endl;
      }else {
        cout << "No" << endl;
      }
    }
    
  }
  
  return 0;
}