Canadian Computing Competition: 2012 Stage 1, Junior #4
Sheldon and Leonard are physicists who are fixated on the BIG BANG theory. In order to exchange secret insights, they have devised a code that encodes UPPERCASE words by shifting their letters forward.
Shifting a letter by ~S~ positions means to go forward ~S~ letters in the alphabet. For example, shifting
B by ~S = 3~ positions gives
E. However, sometimes this makes us go past
Z, the last letter of the alphabet. Whenever this happens we wrap around, treating
A as the letter that follows
Z. For example, shifting
Z by ~S = 2~ positions gives
Sheldon and Leonard's code depends on a parameter ~K~ and also varies depending on the position of each letter in the word. For the letter at position ~P~, they use the shift value of ~S = 3P + K~.
For example, here is how
ZOOM is encoded when ~K = 3~. The first letter
Z has a shift value of ~S = 3 \times 1 + 3 = 6~; it wraps around and becomes the letter
F. The second letter,
O, has ~S = 3 \times 2 + 3 = 9~ and becomes
X. The last two letters become
B. So Sheldon sends Leonard the secret message:
Write a program for Leonard that will decode messages sent by Sheldon.
The input will be two lines. The first line will contain the positive integer ~K~ (~K < 10~), which is used to compute the shift value. The second line of input will be the word, which will be a sequence of uppercase characters of length at most ~20~.
The output will be the decoded word of uppercase letters.
Sample Input 1
Output for Sample Input 1
Sample Input 2
Output for Sample Input 2