A1015 Reversible Primes [质数问题]

#include<cstdio>
#include<iostream>
#include<algorithm>
#include<math.h>
using namespace std;

bool isprime(int n) {
	if (n <= 1) return false;
	int sqr = sqrt(n);
	for (int i = 2; i <= sqr; i++) {
		if (n % i == 0)
			return false;
	}
	return true;
}
int d[100];
int main()
{
	int n, radix;
	while (1)
	{
		cin >> n;
		if (n < 0) break;
		cin >> radix;
		if (isprime(n) == false)
			cout << "No" << endl;
		else
		{
			int len = 0;
			do {
				d[len++] = n % radix;
				n /= radix;
			} while (n != 0);
			for (int i = 0; i < len; i++)
			{
				n = n * radix + d[i];
			}
			if (isprime(n))
				cout << "Yes" << endl;
			else
				cout << "No" << endl;
		}	
	}
	
}