def counts(wrd, q):
'''统计字频'''
for x1 in wrd:
q[x1] += 1
return q
for line in sys.stdin:
_, *words, wd, k = line.strip().split(" ")
a1 = counts(wd, dict.fromkeys(wd, 0)) # 查找词的字频统计
l = []
for w in words:
a2 = counts(w, dict.fromkeys(w, 0)) # 被查找词的字频统计
if wd != w and a1 == a2: # 符合兄弟词的条件
l.append(w)
print(len(l))
if len(l) >= int(k):
print(sorted(l)[int(k)-1])