T6. Less often than others#10078
Given a non-empty string composed solely of letters from the Latin alphabet, identify the letter that occurs the least frequently. Treat uppercase and lowercase letters as equivalent. If there is a tie, select the letter that appears later in the alphabet. Present your answer in uppercase.
The input string's length will not exceed characters.
The input consists of a single line containing the string.
Output a single line with the solution to the problem.
Example 1
Example 2