# This program performs a basic rotation cipher,
# shifting each character in a string by a given amount.

# Prints a rotation cipher of s, shifting each letter in the string
# by the given number of positions in the alphabet.
# pre: s consists entirely of lowercase letters from a-z
# pre: -26 <= amount <= 26
def encode(s, amount):
    for letter in s:
        num = ord(letter) + amount   # shift letter
        if num > ord('z'):           # wrap around if needed
            num -= 26
        elif num < ord('a'):
            num += 26
        print(chr(num), end="")
    print()

def main():
    encode("hello", 3)
    encode("zerglings", 1)
    encode("afshmjoht", -1)
    encode("congratulations", 11)

main()