online_judge_1047

#include<stdio.h>
#include<math.h>
int main()
{
	int n,m,i;
	while(scanf("%d",&n)!=EOF)
	{
		m=(int)sqrt((float)n);
		if(n<=1)
		{
			printf("no
");
			continue;
		}
		for(i=2;i<=m;i++)
			if(n%i==0)
			{
				printf("no
");
				break;
			}
		if(i>m)
			printf("yes
");
	}
	return 0;
}