from sys import stdin
GI = lambda: int(input())
gi = lambda: list(map(int, input().split()))
T = GI()
def solve(id):
    N = GI()
    arr = gi()
    col = 1
    seen = {}
    for i in arr:
        if i in seen and seen[i] != col:
            return "IMPOSSIBLE"
        if i not in seen:
            col += 1
            seen[i] = col
    return " ".join(map(str, sorted(set(arr), key=lambda i: seen[i])))
for i in range(1, T + 1):
    print("Case #%d: %s" % (i, solve(i)))