问题 A: Alive Fossils

Nowcoder Multi-University Training Camp is now holding again. As a contestant, you are a little bit curious about the problem setters. Now you have a list of the problem setters among all the n Nowcoder Multi-University Training Camps, and you are curious about the alive fossil setters, who set problems in all the n camps. Please output the alive fossil setters in the lexicographic order. 

The first line contains one integer n (1 ≤ n ≤ 105 ), denoting the number of Nowcoder Multi-University Training Camps ever held. For each training camp: The first line contains one integer c (1 ≤ c ≤ 105 ), denoting the number of problem setters. Each of the following c lines contains a string containing lowercase letters and digits only, denoting a problem setter in the camp. No problem setters appear more than once in a training camp. It is guaranteed the total length of strings in all training camps does not exceed 106 .

Output a single integer f in the first line, and then output all the f alive fossil setters in the lexicographic order in the following f lines.

2
14
buaa
bit
sunsiyu
uestc
ezec
qcjjfanclub
nfls
oscar114514
jianglyfan
gromah
calabash
lzr010506
gispzjz
roundgod
13
uestc
bit
buaa
gispzjz
roundgod
ynoi
hdu
oscar114514
gromah
calabash
quailty
nfls
sjtu

9
bit
buaa
calabash
gispzjz
gromah
nfls
oscar114514
roundgod
uestc