#include <iostream>
 
using namespace std;
 
int main()
{
   long long x,y=0;
   cin>>x;
 
   for(int i=2;i<=x/2;i++){
        if(x%i==0){
            y=1;
            cout<<"NO";
            break;
        }
 
   }
   if(y==0){
    cout<<"YES";
   }
}
 
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