#include<iostream>#include<cstdio>#include<cstring>#include<string>#include<cmath>#include<cstdlib>#include<algorithm>#include<queue>#include<vector>#include<set>#define N 1000000bool p[N];int n,Max;void prime(){      p[0]=0,p[1]=0,p[2]=1;      Max=(int)sqrt(N*1.0);      for(int i=3;i<=N;i++)           p[i]=i%2==0?0:1;      for(int i=3;i<=Max;i++)            if(p[i])            {                  for(int j=i*i;j<=N;j+=2*i)                        p[j]=0;            }}int main(){      prime();      while(scanf("%d",&n)!=EOF)      {            if(p[n])                  printf("YES\n");            else                  printf("NO\n");      }      return 0;}