#!/usr/bin/python3

def letter_to_int(c):
    return ord(c) - ord('A')

def int_to_letter(i):
    return chr(ord('A') + i)

def continue_from(o):
    global edges
    for i in range(26):
        if edges[o][i] != 0:
            edges[o][i] -= 1
            return i
    return -1  # Neni kam pokracovat.

def cycle_from(o):
    cycle = []
    nextLetter = continue_from(o)
    while nextLetter != -1:
        cycle.append(nextLetter)
        nextLetter = continue_from(nextLetter)
    return cycle  # Je to cyklus, jinde nez v o jsme nemohli skoncit.


M = int(input())
# Vyrobime tabulku hran. cislo edges[i][j] znamena
# cetnost hrany z i do j.
edges = [[0 for i in range(26)] for j in range(26)]
for i in range(M):
    line = input()
    vertices = line.split()
    u = vertices[0][0]  # Prvni pismeno prvniho slova
    v = vertices[1][0]  # Prvni pismeno druheho slova
    edges[letter_to_int(u)][letter_to_int(v)] += 1

# Najdeme pismeno, ze ktereho muzeme zacit.
origin = 0
for i in range(26):
    if sum(edges[i]) != 0:
        origin = i
        break

path = cycle_from(origin)
for i in range(len(path)):
    u = path[i]
    while sum(edges[u]) != 0:
        expansion = cycle_from(u)
        path = path[:i+1] + expansion + path[i+1:]

for i in range(M):
    print(int_to_letter(path[i-1]) + " " + int_to_letter(path[i]))