'''
Given 2 strings, a and b, return a string of the form short+long+short, 
with the shorter string on the outside and the longer string on the inside. 
The strings will not be the same length, but they may be empty ( length 0 ).

For example:

solution("1", "22") # returns "1221"
solution("22", "1") # returns "1221"
'''

def solution(a, b):
    return a+b+a if len(a) <= len(b) else b+a+b
