Background

Chemistry is an interesting subject.I still remember the frustration and bitterness of the first time I studied chemistry.Now it's finally possible for computers to understand chemistry. This question is the missing trim.

Description

Jack Alfred inevitably had some problems when learning matching, and one of them was matching. One of the simpler topics is the lack of trimming. To give an example, such as:

$$\\$$

As above, when methane and oxygen are combusted, A and carbon dioxide are generated, and the missing term is A, which can be obtained through the conservation of elements, and A is $H_2O$.

At this point, Jack Alfred will give you a missing equation for each term, and make sure that only one of the terms is missing, and ask you to output what the missing term is.

Format

Two rows, the first row of substances involved in the reaction, and the second row of substances generated.

Like this：

nA mB kC lD
pF dG tH yJ hX

Your output only needs one line, representing the missing matter.

Like this：

A

Samples

Input1

CH4 2O2
CO2 2X

X indicates the substance to be requested

Output1

H2O

Limitation

No restrictions