/*
 * round 1a problem b
 *
 */

#include <stdio.h>
#include <stdlib.h>

struct barber
{
    unsigned i;
    unsigned long M, t;
};

unsigned long gcd(unsigned long a, unsigned long b)
{
    while (1)
    {
        if (a == 0)
            return b;
        b %= a;
        if (b == 0)
            return a;
        a %= b;
    }
}

unsigned long lcm(unsigned long a, unsigned long b)
{
    unsigned long tmp = gcd(a, b);
    return tmp ? (a / tmp * b) : 0;
}

unsigned long lcmbarber(unsigned c, struct barber* v)
{
    unsigned long m;
    unsigned i;

    m = 1;
    for (i = 0; i < c; ++i)
        m = lcm(m, v[i].M);

    return m;
}

int cmp(const struct barber** b1, const struct barber** b2)
{
    if ((*b1)->t < (*b2)->t)
        return -1;
    if ((*b1)->t > (*b2)->t)
        return 1;
    if ((*b1)->i < (*b2)->i)
        return -1;
    return 1;
}

int main(int argc, char* argv[])
{
    unsigned T, x;

    scanf(" %u ", &T);

    for (x = 1; x <= T; ++x)
    {
        unsigned long B, N, y, i, m, asd;
        struct barber* b;
        struct barber** bp;

        scanf(" %lu %lu ", &B, &N);
        b = malloc(B * sizeof(struct barber));
        bp = malloc(B * sizeof(struct barber*));

        for (i = 0; i < B; ++i)
        {
            b[i].i = i+1;
            b[i].t = 0;
            scanf(" %lu ", &b[i].M);
            bp[i] = &b[i];
        }

        /* optmize!!1!1ONE! */
        m = lcmbarber(B, b);
        asd = 0;

        for (i = 0; i < B; ++i)
            asd += m / b[i].M;

        while (asd < N)
            N -= asd;

        while (1)
        {
            unsigned long t;
            qsort(bp, B, sizeof (struct barber*), (int(*)(const void*, const void*))&cmp);

            i = 0;

            if (N == 1)
            {
                y = bp[i]->i;
                break;
            }

            t = bp[0]->t;

            for (i = 0; i < B; ++i)
                bp[i]->t -= t;

            for (i = 0; (i < B) && (N > 1) && (bp[i]->t == 0); ++i, --N)
                bp[i]->t = bp[i]->M;
        }

        printf("Case #%u: %lu\n", x, y);

        free(bp);
        free(b);
    }

    return 0;
}