tests = int(input())

for case in range(1, tests+1):
    m, r, n = list(map(int, input().split()))
    positions = list(map(int, input().split()))
    earliest_location = 0
    current_position = -1
    current_amount = 0
    bad = False
    while earliest_location < m:
        # print(earliest_location, current_position, current_amount)
        if current_position + 1 == len(positions):
            bad = True
            break
        next_position = current_position + 1
        while (
            next_position < len(positions) and
            positions[next_position] - r <= earliest_location
        ):
            next_position += 1
        if next_position - 1 <= current_position:
            bad = True
            break
        earliest_location = positions[next_position - 1] + r
        current_amount += 1
        current_position = next_position - 1
    if bad:
        print(f"Case #{case}: IMPOSSIBLE")
    else:
        print(f"Case #{case}: {current_amount}")