Code in c language

Please enter a valid string: 5tring5 Please enter a valid string: String You entered: STRING which is size 6 The ciphered string is EFDUZS, what is the cipher key? 0 The cipher key is between 1 and 25 try again: 3 The cipher string shifted back 3 is BCARWP, incorrect! The ciphered string is EFDUZS, what is the cipher key? 11 The ciphered string shifted back 11 S TUSJOH, incorrect! The ciphered string is EFDUzs, what is the cipher key?: 12 The ciphered string shifted back 12 is STRING, that's correct! The sum of the ascii in STRING is 471 ./a.out Enter the size of the string: o Please enter again: 18 Please enter the string : ^1$e01$ Please enter a valid string: baseball You entered: BASEBALL which is size 8 The ciphered string is YXPBYXII, what is the cipher key: -10 The cipher key is between 1 and 25, try again: 30 The cipher key is between 1 and 25, try again: 9 The cipher string shifted back 9 s POGS POZZ, incorrect! The ciphered string is YXPBYXII, what is the cipher key: 1 The cipher string shifted back 1 is , ncorrect ! The ciphered string is YXPBYXII, what is the cipher key: 23 The ciphered string shifted back 23 is BASEBALL, that's correct! The sum of the ascii in BASEBALL is 566 Bonus I have done the above without using ctype.h library