"""
Google Code Jam Farewell Round C - Problem A

Author  : chaotic_iak
Language: PyPy (Python 3.9.10)
"""

################################################### SOLUTION

def initialize_solution():
    ...

def solve(prev, char, now):
    #print(prev, now)
    c = ord(prev[char])-64
    if prev[char] == "@": return "".join(chr(64+i) * now[i] for i in range(27)) + "@"
    has_more = any(now[i] > 0 for i in range(c+1, 27))
    if now[c] == 0 and not has_more: return -1
    if now[c]:
        now[c] -= 1
        res = solve(prev, char+1, now)
        now[c] += 1
        if res != -1: return prev[char] + res
    if not has_more: return -1
    i = min(i for i in range(c+1, 27) if now[i])
    now[i] -= 1
    res = solve("@", 0, now)
    now[i] += 1
    return chr(i+64) + res

def main():
    p, = read() if True else [100]
    S = read(str) if True else ["A"*i + "B"*(99-i) + "C" for i in range(100)]
    A = []
    for s in S:
        inven = [0]*27
        for c in s:
            inven[ord(c)-64] += 1
        A.append(inven)
    ans = []
    curr = "@"
    for a in A:
        nex = solve(curr, 0, a)
        if nex == -1: return "IMPOSSIBLE"
        ans.append(nex[:-1])
        curr = nex
    write("POSSIBLE")
    write(*ans)

############################################### PROBLEM TYPE

HAS_TESTCASES = True
INTERACTIVE = False
INTERACTIVE_WRONG_ANSWER = ""

#################################################### HELPERS

import sys

def read_str():
    ipt = input().strip()
    if INTERACTIVE and ipt == INTERACTIVE_WRONG_ANSWER:
        sys.exit()
    return ipt

def read(mapping=int):
    ipt = input().strip()
    if INTERACTIVE and ipt == INTERACTIVE_WRONG_ANSWER:
        sys.exit()
    return list(map(mapping, ipt.split()))

def write_str(obj, end="\n"):
    global OUTPUT
    OUTPUT.append(obj + end)

def write(*obj, sep=" ", end="\n"):
    global OUTPUT
    OUTPUT.append(sep.join(map(str, obj)) + end)

def flush():
    global OUTPUT
    print("".join(OUTPUT), end="", flush=True)
    OUTPUT = []

def solve_testcase():
    result = main()
    if result is not None:
        write(result)

OUTPUT = []
initialize_solution()
if HAS_TESTCASES:
    TOTAL_CASES = int(input())
else:
    TOTAL_CASES = 1
for CASE_NUMBER in range(TOTAL_CASES):
    write("Case #" + str(CASE_NUMBER+1) + ": ", end="")
    solve_testcase()
flush()

READ_FROM_FILE = ""