Filter Non-Letter Characters

Given a string S' that was originally formed by a sequence of only uppercase or lowercase letters, some additional non-letter characters (digits, punctuation, etc.) have been inserted into S at arbitrary positions. These inserted characters are guaranteed not to be letters and are present on a standard keyboard. Your task is to remove all non-letter characters from S' and output the resulting string S.

For example, if S' = "abc123DEF", then S = "abcDEF".

inputFormat

The input consists of a single line containing the string S'. This string may include letters, digits, punctuation, and other symbols available on a keyboard.

outputFormat

Output the string formed by removing all non-letter characters from S'. Only uppercase and lowercase letter characters should be preserved, in the same order as they appear in the input.

sample

abc123DEF

abcDEF