"Sensual prime number" refers to a pair of prime numbers of the form (p, p+6). The reason for this name is that "six" is called "sex" in Latin (that is, "sexy" in English). (Original excerpt from http://mathworld.wolfram.com/SexyPrimes.html)
Now given an integer, please judge whether it is a sexy prime number.
Input format:
The input gives a positive integer N (≤108) in one line.
Output format:
If N is a sexy prime number, output it on one line Yes, and output another sexy prime number paired with N on the second line (if such number is not unique, output the smaller one). If N is not a sexy prime number, output it in one line No, and then output the smallest sexy prime number greater than N in the second line.
Input sample 1:
47
Sample-1: "> Sample-1: "> Output Sample 1:
Yes
41
Input sample 2:
21
Output sample 2:
No
23
The point to note is that when judging a prime number, it should be noted that the smallest prime number is 2, and anything less than 2 is not a prime number. In addition, when N is not a sexy prime number, when looking for a sexy prime number larger than N, the number M found may be the larger one in the sexy prime number pair, so isPrime(i-6) should also be considered
#include<cstdio>
#include<cmath>
#include<iostream>
using namespace std;
bool isPrime(int num);
int main(){
int N;
cin>>N;
if(isPrime(N) && isPrime(N-6))
cout<<"Yes"<<endl<<N-6<<endl;
else if(isPrime(N) && isPrime(N+6))
cout<<"Yes"<<endl<<N+6<<endl;
else{
for(int i=N+1;;i++){
//i本身是质数，且i-6 或者 i+6 也是质数
if(isPrime(i)&&(isPrime(i+6)||isPrime(i-6))){
cout<<"No"<<endl<<i<<endl;
break;
}
}
}
return 0;
}
bool isPrime(int num){
if(num<2)
return false;
int n=sqrt(num);
for(int i=2;i<=n;i++)
if(num%i==0)
return false;
return true;
}