Problem Statement

Given are $N strings S_1, S_2, \dots, S_N$.
Each of these is a non-empty string consisting of lowercase English letters, with zero or one ! added at the beginning.
We say a string T to be unsatisfied when it matches one of $S_1, S_2, \dots, S_N$ regardless of whether we add an ! at the beginning of T.
Determine whether there exists an unsatisfied string. If so, present one such string.

Input

Input is given from Standard Input in the following format:
N
S_1
$\vdots$
S_N

Output

If there exists an unsatisfied string, print one such string.
If there is no unsatisfied string, print satisfiable.

Constraints

• $1 \le N \le 2 \times 10^5$
• $1 \le |S_i| \le 10$
• S_i is a non-empty string consisting of lowercase English letters, with zero or one ! added at the beginning.

Sample Input 1

6
a
!a
b
!c
d
!d

Sample Output 1

a

a matches S_1 as is, and it matches S_2 when we add an !, so it is unsatisfied.
Besides that, d will also be accepted.

Sample Input 2

10
red
red
red
!orange
yellow
!blue
cyan
!green
brown
!gray

Sample Output 2

satisfiable

见题面 Input 部分

见题面 Output 部分