poj 2635 The Embarrassed Cryptographer

//poj 2635 The Embarrassed Cryptographer
#include<iostream>
#include<cmath>
#include<cstdio>
#include<cstring>
#include<algorithm>
#define M(a) memset(a,0,sizeof a)
#define fo(i,j,k) for(i=j;i<=k;i++)
using namespace std;
const int mxn=1e6;
char k[105];
int pri[mxn+5],l;
bool vis[mxn+5];
inline int read()
{
int x=0,f=1;char ch=getchar();
while(ch>'9'||ch<'0'){if(ch=='-')f=-1;ch=getchar();}
while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}
return x*f;
}
inline void shai()
{
int i,j;
fo(i,2,mxn)
{
if(!vis[i]) pri[++pri[0]]=i;
fo(j,1,pri[0])
{
if(i*pri[j]>mxn) break;
vis[i*pri[j]]=1;
if(i%pri[j]==0) break;
}
}
}
int main()
{
int i,j;
shai();
while(scanf("%s",k+1))
{
l=read();
if(!l) return 0;
int len=strlen(k+1);
bool flag=0;
for(i=1;i<=pri[0] && pri[i]<l;i++)
{
int now=0;
for(j=1;j<=len-2;j+=3)
now=(now*1000+100*(k[j]-'0')+10*(k[j+1]-'0')+k[j+2]-'0')%pri[i];
if(j==len-1) now=(now*100+10*(k[len-1]-'0')+k[len]-'0')%pri[i];
else if(j==len) now=(now*10+k[len]-'0')%pri[i];
if(now==0)
{
flag=1;
printf("BAD %d\n",pri[i]);
break;
}
}
if(!flag) printf("GOOD\n");
}
return 0;
}