Crypto Wars: Missing Number

Our fleet managed to get one of the enemy's top-secret codes from the remains of its fallen ship. The codes were immediately sent over to our code-breaking base over at Bleckley Park ;) for analysis. The team found that each code contains 25 numbers with one missing. The missing number corresponds to a letter in the English alphabet. Your job is to find a more efficient Method of decrypting the messages by digitizing the process.

Write a function that takes a list, detects the missing number (in the list), and returns its corresponding letter.

Examples

decrypt([19, 12, 14, 21, 22, 3, 11, 20, 9, 16, 24, 17, 2, 10, 13, 18, 7, 8, 4, 5, 1, 6, 25, 23, 26]) ➞ "O"
# The missing number is 15.

decrypt(24, 12, 2, ..., 25) ➞ "N"
# The missing number is 14.

decrypt(24, 12, 2, ..., 25) ➞ "P"
# The missing number is 16.

Notes

• The list will only contain positive integers from 1 to 26 with one missing.
• There will be no duplicate numbers.
• Return the capital letter.