Problem Description

Encode a string as character-frequency pairs sorted by character. Format: each character followed by its frequency count.

Input Format

A single string containing lowercase letters.

Output Format

Encoded string with characters and frequencies in alphabetical order.

Constraints

• 1 ≤ string length ≤ 1000

• String contains only lowercase letters

• Format: character + frequency (e.g., a3b1)

• Sort characters alphabetically

• Include all characters that appear

Sample Input/Output

Explanation

Character frequencies: a=3, b=1, n=2. Sorted alphabetically: a3b1n2.