35

from random import *
n=int(input())
a=n*[0]
for i in range(n):
    a[i]=input()
z=int(n/2)
for i in range(z):
    b=randint(0,n-1)
    c=randint(0,n-1)
    while a[b]==0:
        b=randint(0,n-1)
    while a[c]==0 or a[b]==a[c]:
        c=randint(0,n-1)
    print(a[b],a[c])
    a[b]=0
    a[c]=0