题目

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 (<) and D (1<D≤10), you are supposed to tell if N is a reversible prime with radix D.

输入

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.

输出

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

样例输入 

73 10
23 2
23 10
-2

样例输出 

Yes
Yes
No

题意理解

题目大意是给你一个数，判断一下这个数是否是素数，如果不是素数那么可以直接输出No了，如果是素数，那么将这个数字转换成D进制的数的逆序，再判断一下是不是素数，如果是，则输出Yes，不是就输出No。那么我们直接根据题意模拟一下即可。水题。

代码 

#include<bits/stdc++.h>
using namespace std;
bool prime(int nu){
    if(nu<2)return false;
    for(int i=2;i<=nu/i;i++){
        if(nu%i==0)return false;
    }
    return true;
}
bool check(int nu,int d){
    if(!prime(nu))return false;
    int x=nu;int sum=0;
    while(x){
        int c=x%d;
        sum=sum*d+c;
        x/=d;
    }
    if(!prime(sum))return false;
    else return true;
}
void solve(){
    int n,m;
    while(~scanf("%d",&n)&&n>0){
        scanf("%d",&m);
        if(check(n,m))puts("Yes");
        else puts("No");
    }
}
int main(){
    solve();
    return 0;
}