409575: GYM103637 C Crossed out letter

Consider string $$$s$$$. Let's call $$$s$$$ with some single character removed – $$$s_0$$$, and without some, possibly another, character – $$$s_1$$$. You are given $$$s_0$$$ and $$$s_1$$$, find any suitable string $$$s$$$ or determine, that there are none.

The first line of the input data contains one string $$$s_0$$$ consisting of lowercase English letters.

The second line of the input data contains one string $$$s_1$$$ consisting of lowercase English letters.

$$$$$$ 1 \le |s_0|, |s_1| \le 3 \cdot 10^5 $$$$$$

$$$$$$ |s_0| = |s_1| $$$$$$

Print a single line $$$s$$$ consisting of lowercase English letters or "IMPOSSIBLE" (in capital letters, without quotes).

abacaa
aacaba

abacaba

bsuir
openx

IMPOSSIBLE

In the first test case, removing from "abacaba" second character "b" we get $$$s_0=$$$"abacaa", and removing "abacaba" first character "b", we get $$$s_1=$$$"aacaba".

In the second test case there isn't any string $$$s$$$.