Python 3:In this problem, your input file will contain a number of ciphertext and key pairs, separated by a space. You may assume that the ciphertext contains only uppercase letters. However, it is possible that the key may be missing, and your program should handle this case.

The ciphertext has been encrypted by shifting letters in the alphabet by the amount specified by the key. The word HELLO with key = 2 becomes JGNNQ. Letters should wrap around, so PIZZA with key = 1 becomes QJAAB. If the key is missing, your program should output a message "Missing key!".

code.txt

CLGUBA 13

JGNNQ

ZKADQSZ 1

OQJ 4

AKNSR 2

NGBOXKLBMR 7

sample output

Enter the input filename: code.txt PYTHON Missing key! ALBERTA SUN CMPUT UNIVERSITY