Getting wrong answer on online judges [on hold]

I have written the following code for the http://ift.tt/1yQ6C2s, which I have tested thoroughly. I have tried running it on all the corner cases and also on some very typical inputs like 0 and 1. It ran successfully each time, but I'm still getting WA. What might be the reason?

#include<stdio.h>

int main()
{
    int t;
    scanf("%d",&t);
    while(t--){
        int a,end=1,i,unit[500],temp=1;
        scanf("%d",&a);
        long long b;
        scanf("%lld",&b);
    if(a==1){
        printf("1\n");
        continue;
    }
    if(b==0){
        printf("1\n");
        continue;
    }
    unit[0]=1;          
    bool goOn=true,marker=false;
    while(goOn){
        temp*=a;
        for(i=0; i<end; i++){
            if(unit[i]==(temp%10) && (temp%10)!=1)
                marker=true;
        }
        if(marker)
            goOn=false;
        if(!marker){
            unit[end]=(temp%10);
            end++;
        }
    }

    int tmp=b%(end-1);
    if(tmp==0)
        printf("%d\n",unit[(end-1)]);
    else
        printf("%d\n",unit[(tmp)]);
}
return 0;
}

Which might be the test case that I might be missing?