n = int(input())
u_list = [input().strip() for _ in range(n)]
used = set()
splits = []

possible = True

for u in u_list:
    # Try split into S (1 char) and T (2 chars)
    s1 = u[0]
    t1 = u[1:]
    if s1 not in used and t1 not in used:
        used.add(s1)
        used.add(t1)
        splits.append((s1, t1))
    else:
        # Try split into S (2 chars) and T (1 char)
        s2 = u[:2]
        t2 = u[2]
        if s2 not in used and t2 not in used:
            used.add(s2)
            used.add(t2)
            splits.append((s2, t2))
        else:
            possible = False
            break

if possible:
    for s, t in splits:
        print(f"{s} {t}")
else:
    print("Impossible")