Description

The young and very promising cryptographer Odd Even has implemented the security module of a large system with thousands of users, which is now in use in his company. The cryptographic keys are created from the product of two primes, and are believed to be secure because there is no known method for factoring such a product effectively.
What Odd Even did not think of, was that both factors in a key should be large, not just their product. It is now possible that some of the users of the system have weak keys. In a desperate attempt not to be fired, Odd Even secretly goes through all the users keys, to check if they are strong enough. He uses his very poweful Atari, and is especially careful when checking his boss' key.

Input

Output

Sample Input

143 10
143 20
667 20
667 30
2573 30
2573 40
0 0

Sample Output

GOOD
BAD 11
GOOD
BAD 23
GOOD
BAD 31

題目的大意是：給一個很大的數(shù)K，和一個普通的整數(shù)L，問K有沒有小于L的質(zhì)因子，有則輸出“BAD 那個因子”，否則輸出“GOOD”。

首先，明顯當(dāng)然要打一個素數(shù)表了。
接下來就是關(guān)鍵部分了，讀入K，把K轉(zhuǎn)成千進(jìn)制。把數(shù)字往大進(jìn)制轉(zhuǎn)換能夠加快運(yùn)算效率。千進(jìn)制的性質(zhì)與十進(jìn)制相似。例如，1234567890轉(zhuǎn)成千進(jìn)制，就變成了：[1][234][567][890]。

然后再從小到大枚舉每一個素數(shù)，并對其進(jìn)行高精度求余就行了。

下面是關(guān)鍵部分的一些代碼：

int divide(int div) //高精度求余。 
{
    int i,ans=0;
    for(i=la-1;i>=0;i--)
        ans=(ans*1000+a[i])%div;
    return ans;    
}

void makeprime() //建立素數(shù)表。 
{
    int i,j,isprime,k,p=3;
    for(i=6;i<N;i++)
    {
        isprime=1;
        k=(int)sqrt(i);    
        for(j=0;j<p;j++)
        {
            if(prime[j]>k+1)
                break;
            if(i%prime[j]==0)
            {
                isprime=0;
                break;
            }    
        }
        if(isprime) prime[p++]=i;    
    }    
}

        len=strlen(s);
        for(i=0;i<len;i++) //轉(zhuǎn)化為千進(jìn)制。 
        {
            t=(len-i+2)/3-1;
            a[t]=a[t]*10+s[i]-'0';
        }
        la=(len+2)/3;