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 B .

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 A and B . So Sheldon sends Leonard the secret message: FXAB

Write a program for Leonard that will decode messages sent by Sheldon.

Input Specification

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 \(20\) .

Output Specification

The output will be the decoded word of uppercase letters.

Sample Input 1

3
FXAB

Output for Sample Input 1

ZOOM

Sample Input 2

5
JTUSUKG

Output for Sample Input 2

BIGBANG