def num_painted_segments(s):
    lt = 0
    rt = len(s)
    for x in s:
        if x == 'B':
            break
        lt += 1
    for x in s[::-1]:
        if x == 'B':
            break
        rt -= 1
    return rt - lt

# Main function
t = int(input())
for _ in range(t):
    n = int(input())
    s = input()
    print(num_painted_segments(s))