Characters Common To All Strings

Write a function all_common(strings) that takes a list of strings and returns a string made of the characters that appear in every one of them. The characters must be in ascending (sorted) order and each one appears only once. If the list is empty, return the empty string ''.

Example

all_common(['apple', 'ample', 'maple'])  ->  'aelp'
all_common(['abc', 'xyz'])               ->  ''

Your task

Implement this function:

def all_common(strings: list) -> str:

Write the function only — the arguments are read for you and the return value is printed automatically.

Arguments arrive as one Python literal per line, in this order: strings.

Example

Input

['apple', 'ample', 'maple']

Output

'aelp'