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

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