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

int issu(int n)
{
	int t=sqrt(n);
	int flag=1;//judgement
	for(;t<n/2+1;t++)
		if(n%t==0)
		{
			flag=0;
			break;
		}
	return flag;
}
int main()
{
	int n;
	while(cin>>n)
	{
		if(n<=1)
		cout<<"no"<<endl;
	 else
	  {
		if(issu(n))
			cout<<"yes"<<endl;
		else
		    {
			cout<<"no"<<endl;
	    	}
	   }
	}
	return 0;
}