An old encryption technique involves replacing each letter in a message with another letter that is a fixed number of positions later in the alphabet (when the replacement goes past the letter Z, the cipher wraps around to the beginning of the alphabet.) Write a program that encrypts a message using this technique. The user will enter the message to be encrypted and the shift amount. Assume the message does not exceed 80 characters. Characters other than letters should be left unchanged. Lower-case letters remain lower-case when encrypted, and upper-case letters remain upper-case. To handle the wrap around problem, use the expression ((ch-'A') n)& 'A' to calculate the encrypted version of an upper-case letter (where ch sores the letter and n stores the shift amount). Use a similar expression for lower-case letters.