#include<stdio.h>
int main()
{
    int prime(int n);
    int n;
    scanf("%d",&n);
    if(prime(n))
        printf("yes");
    else
        printf("no");
    return 0;
}
int prime (int n)

{
    int flag=1,i;
    for (i=2;i<n/2;i++)
        if (n%i==0)
        flag = 0;
    return flag;
}