#include<iostream> // cin\cout\endl #include<cstdio> //scanf()\printf() #include<cstring> // strcpy()\strcat()\strcmp()\strlen()\memset() #include<cmath> //sqrt()\pow()\abs()\ceil()\floor()\max()\min() using namespace std; int main(){ int n,i=2; cin>>n; while(i<=sqrt(n)){ if(n%i==0){ cout<<"NO";return 0; } i++; } cout<<"YES"; return 0; }