divisible or not

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
int main()
{
    unsigned long long int t,a,b,d,e;
    scanf("%llu",&t);
    for (int i=1;i<=t;i++)
    {
        scanf("%llu%llu",&a,&b);
        a=abs(a);
        b=abs(b);
        int s=0;
        e=a;
        while (e!=0)
        {
            s++;
            e=e/10;
        }
        int arr[s];
        for (int j=s-1;j>=0;j--)
        {
            arr[j]=a%10;
            a=a/10;
        }
        long long int c=0;
        for (int j=0;j<s;j++)
        {
            c=(c*10)+arr[j];
            c=c%b;
        }
        if (c==0) printf("Case %d: divisible\n",i);
        else printf("Case %d: not divisible\n",i);
    }
    return 0;
}