#!/usr/bin/env python3.8
import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines
import itertools
import numpy as np
from scipy.sparse.csgraph import connected_components
N = int(readline())
if N > 52:
    print('Impossible')
    exit()


words = [readline().rstrip().decode() for _ in range(N)]
AB = []

for i, j in itertools.product(range(N), repeat=2):
    if i == j:
        continue
    S = words[i]
    T = words[j]
    if S[0] == T[0] or S[1:] == T[1:]:
        AB.append((2 * i, 2 * j + 1))
    if S[-1] == T[-1] or S[:2] == T[:2]:
        AB.append((2 * i + 1, 2 * j))
    if S[0] == T[-1] or S[1:] == T[:2]:
        AB.append((2 * i, 2 * j))
    if S[-1] == T[0] or S[:2] == T[1:]:
        AB.append((2 * i + 1, 2 * j + 1))

G = np.zeros((N + N, N + N), np.bool)
for a, b in AB:
    G[a, b] = 1

C, comp = connected_components(G, directed=True, connection='strong')
graph = [[] for _ in range(C)]
in_deg = [0] * C
for a, b in AB:
    ca = comp[a]
    cb = comp[b]
    if ca == cb:
        continue
    graph[ca].append(cb)
    in_deg[cb] += 1

order = []
deg_0 = [i for i, x in enumerate(in_deg) if x == 0]
while deg_0:
    v = deg_0.pop()
    order.append(v)
    for w in graph[v]:
        in_deg[w] -= 1
        if not in_deg[w]:
            deg_0.append(w)
rank = [0] * C
for i, x in enumerate(order):
    rank[x] = i

answers = []
for i in range(N):
    v = 2 * i
    w = 2 * i + 1
    rv = rank[comp[v]]
    rw = rank[comp[w]]
    if rv == rw:
        print('Impossible')
        exit()
    if rv > rw:
        answers.append((words[i][0], words[i][1:]))
    else:
        answers.append((words[i][:2], words[i][2]))

for a, b in answers:
    print(a,b)