hdu 2161 Primes

#include<stdio.h>int a[16001];int main(){int i,j;for(i=2;i<=800;i++){if(a[i]==1)continue;for(j=i+i;j<=16000;j=j+i)a[j]=1;}a[1]=a[2]=1;i=1;while(scanf("%d",&j),j>0){if(a[j]==0)printf("%d: yes\n",i++);else printf("%d: no\n",i++);}return 0;}