OJ Board

I have submitted prime cut. But the machine give me wrong answer.
What's the problem? #include<stdio.h>


int main()
{
char a[100000];
long long i,p,q,c,d,x,j,z=1,flage,temp;


while(scanf("%s",a)!=EOF)
{
if(a=="\0")
break;
scanf("%lld",&x);
printf("Case %lld:\n",z++);
for(j=1;j<=x;j++)
{
XY ...