Find the Missing Letter

You are given a string of consecutive letters with one missing letter. The string will always consist of letters from a single alphabetic case (either all lowercase or all uppercase) and will have at least two characters.

Your task is to find and print the missing letter in the sequence.

Examples:

• If the input is abcdf, the missing letter is e.
• If the input is OQRS, the missing letter is P.

Note: The input will be provided via standard input (stdin) and the result should be printed to standard output (stdout).

inputFormat

The input consists of a single line containing a string of consecutive letters with one letter missing. There are no spaces between the letters.

Example: abcdf

outputFormat

Output the missing letter as a single character on a line.

Example Output: e

## sample

abcdf

e