Generate Login

给定两个用空格分隔的字符串，分别取两字符串的任意非空前缀，将两前缀合并为一个新的字符串，求可行字典序最小的字符串。

The preferred way to generate user login in Polygon is to concatenate a prefix of the user's first name and a prefix of their last name, in that order. Each prefix must be non-empty, and any of the prefixes can be the full name. Typically there are multiple possible logins for each person. You are given the first and the last name of a user. Return the alphabetically earliest login they can get (regardless of other potential Polygon users). As a reminder, a prefix of a string $ s $ is its substring which occurs at the beginning of $ s $ : "a", "ab", "abc" etc. are prefixes of string "{abcdef}" but "b" and 'bc" are not. A string $ a $ is alphabetically earlier than a string $ b $ , if $ a $ is a prefix of $ b $ , or $ a $ and $ b $ coincide up to some position, and then $ a $ has a letter that is alphabetically earlier than the corresponding letter in $ b $ : "a" and "ab" are alphabetically earlier than "ac" but "b" and "ba" are alphabetically later than "ac".

The input consists of a single line containing two space-separated strings: the first and the last names. Each character of each string is a lowercase English letter. The length of each string is between 1 and 10, inclusive.

Output a single string — alphabetically earliest possible login formed from these names. The output should be given in lowercase as well.

harry potter

hap

tom riddle

tomr