B.py

def solve(l):
    r = sorted(enumerate(l), key=lambda x:x[1])
    for i, (sigma, _) in enumerate(r):
        if (sigma - i) % 2 != 0:
            return i
    else:
        return "OK"

T = int(input())
for i in range(T):
    _ = input()
    l = [int(e) for e in input().split()]
    print("Case #{}: {}".format(i+1, solve(l)))