21735_A+B

The Research Institute of Given Strings (RIGS) is a well-known place where people investigate anything about strings. Peter works in the department of string operations of RIGS. His department invents different ways to add, multiply, divide strings and even to take logarithm of string based on another one.

Peter's task is to invent an operation of sum of two given strings. The current Peter's proposal allows to add only strings of the same length n. To do this, Peter takes the set of all strings of length n over a fixed alphabet. Then Peter sorts all taken strings, thus obtaining a sorted sequence of strings T. Let's denote the length of T as M, and enumerate the elements of this sequence as T₀, T₁ ... T_M-1. Now Peter says that the sum of two strings A = T_a and B = T_b is a string C = T_c where c = (a + b) mod M.

Your task is to find the sum of two given strings A and B over the alphabet of small English letters.

The input file consists of two lines containing strings A and B of the same length. Both strings consist of small letters of English alphabet. The length of each string doesn't exceed 100000.

Output the sum of strings A and B.

Sample #1
neerc
neerc

Sample #2
z
y

Sample #1
aijie

Sample #2
x