# include<iostream> # include<cstdio> # include<iomanip> using namespace std; int main(){ int N,f=1; cin>>N; for(int i=2;i*i<=N;i++){ if(N%i==0) { f=0; break;} } if(N==1) cout<<"NO";return 0; if(f==1) cout<<"YES"; else cout<<"NO"; return 0; }