def rearrange(left, si):
    cnt = [0] * 26
    for ci in si:
        cnt[ord(ci) - ord('A')] += 1

    back = False    
    ll = len(left)
    ls = len(si)
    res = []
    for i in range(ll):
        if i == ls:
            back = True
            break
        li = ord(left[i]) - ord('A')
        if cnt[li] >= 1:
            res.append(li)
            cnt[li] -= 1
            continue

        for alp in range(li+1,26):
            if cnt[alp] >= 1:
                res.append(alp)
                cnt[alp] -= 1
                break
        else:
            back = True
        break

    if back:
        while len(res):
            last = res.pop()
            cnt[last] += 1
            for alp in range(last+1,26):
                if cnt[alp] >= 1:
                    res.append(alp)
                    cnt[alp] -= 1
                    break
            else:
                continue
            break
        else:
            return ''
    
    for alp in range(26):
        for _ in range(cnt[alp]):
            res.append(alp)
    
    res = [chr(ord('A') + x) for x in res]
    res = ''.join(res)
    return res

def solve_a(p,s):
    ans = []
    left = ''
    for i in range(p):
        res = rearrange(left, s[i])
        if res == '':
            return []
        ans.append(res)
        left = res
    
    return ans   

def solve(p,s):
    if p > 3:
        return []
    
    l = len(s)
    if p == 2:
        for i in range(1,l):
            s1 = s[:i]
            s2 = s[i:]
            res = solve_a(p, [s1,s2])
            if not res:
                return [s1,s2]
        
        return []
    
    for i in range(1,l-1):
        s1 = s[:i]
        for j in range(i+1,l):
            s2 = s[i:j]
            s3 = s[j:]
            res = solve_a(p, [s1,s2,s3])
            if not res:
                return [s1,s2,s3]
        
    return []

# import sys
# import os
# f = open('./input.txt', 'r')
# sys.stdin = f
    
t = int(input())
for i in range(1,t+1):
    p,s = input().split()
    p = int(p)
    ans = solve(p, s)
    if ans:
        print(f'Case #{i}: POSSIBLE')
        print(*ans)
    else:
        print(f'Case #{i}: IMPOSSIBLE')