Write a program to read in a list of integers and determine whether or not each number is prime. A number, n, is prime if its only divisors are 1 and n. For this problem, the numbers 1 and 2 are not considered primes. 

Input

Each input line contains a single integer. The list of integers is terminated with a number<= 0. You may assume that the input contains at most 250 numbers and each number is less than or equal to 16000. 

Output

The output should consists of one line for every number, where each line first lists the problem number, followed by a colon and space, followed by "yes" or "no". 

Sample Input

1
2
3
4
5
17
0

Sample Output

1: no
2: no
3: yes
4: no
5: yes
6: yes

题意：给出几个数判断一下是不是素数，是的话输出yes，不是的话输出no。

思路:用素数打表法，当一个数是素数时，它的倍数肯定不是素数，然后注意一下这个题是小于等于0时结束。代码如下：

#include<stdio.h>
#include<string.h>
int a[16010];
int main()
{
    int n,i,j,k=1;
    memset(a,0,sizeof(a));
    for (i = 2; i<=16010; i++)
    {
        if (a[i]==0)  //0是素数
        {
            for (j=i+i; j<=16010; j+=i)
                a[j]=1;
        }
    }
    a[1]=1;a[2]=1;
    while(~scanf("%d",&n))
    {
        if(n<=0)
            break;
        if(a[n]==0)
            printf("%d: yes\n",k++);
        else
            printf("%d: no\n",k++);
    }
    return 0;
}