import java.util.Scanner;
class Prime {
static int prime(int n){
int su_flag=1;
if(n==1) su_flag=0;
else if(n==2) su_flag=1;
else
{
for(int i=2;i<n-1;i++)
{
if(n%i==0)
{su_flag=0;break;}
}
}
//System.out.println(su_flag);
if(su_flag==1) return 1;
else return 0;
}
}
public class Main
{
public static void main(String [] args){
Scanner in=new Scanner(System.in);
int n=in.nextInt();
int m=Prime.prime(n);
if(m==1) System.out.println("YES");
else System.out.println("NO");
}
}
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