for _ in range(int(input())):
    N=int(input())
    S=list(input())

    last = "-"
    p,k = 0,0
    for i in S:
        if last == i:
            continue
        last = i
        if i == "P":
            p += 1
        elif i == "K":
            k += 1
    
    if p<=k:
        print("K")
    else:
        print("P")