Segregate Letters and Digits

This problem requires you to process a given string and segregate its alphabetic and numeric characters. Specifically, you are to output a new string that contains all the letters from the input (in the order they appear) followed by all the digits (in the order they appear). Any other characters, such as punctuation or spaces, should be ignored.

Formally, given a string s, you need to compute a result string r such that

\( r = L + D \)

where \( L \) is the concatenation of all letters in s (\( s_i \) satisfying \( s_i \in [a-zA-Z] \)) and \( D \) is the concatenation of all digits in s (\( s_i \) satisfying \( s_i \in [0-9] \)).

Maintain the relative order of the letters and digits as they appear in the input.

inputFormat

The input consists of a single line containing a string s that may include letters, digits, spaces, and other special characters.

outputFormat

Output a single line containing the modified string where all letters come first (in their original order) followed by all digits (in their original order). All other characters should be discarded.

a1b2c3

abc123