Given strings of lowercase letters, compute the lexicographically largest string that is a subsequence of all strings.

String is a subsequence of string if can be obtained by deleting some of the letters in . It is not required to delete any letters.

String is lexicographically larger than if is a prefix of or, given that index is the first mismatch in strings and , the th character of is larger than the th character of .

#### Constraints

The sum of the lengths of all strings will be at most .

All strings will only contain lowercase letters.

#### Input Specification

The first line contains a single positive integer, .

The next lines each contain a string of lowercase letters. The string is guaranteed to contain at least one letter.

#### Output Specification

Output the lexicographically largest common subsequence. If no nonempty subsequence exists, output `-1`

.

#### Sample Input 1

```
2
quantum
xyene
```

#### Sample Output 1

`n`

#### Sample Input 2

```
1
cba
```

#### Sample Output 2

`cba`

#### Sample Input 3

```
3
a
ab
c
```

#### Sample Output 3

`-1`

## Comments