Prisoner X has a value Y, he chooses Z.
X, Y, Z lies between 1 to 4.
K is a specific non-negative integer.
Formula: (X - 1) + 3 (Y - 1) + (Z - 1) = 4 (K - 1)
Z = 4 (K - 1) - (X - 1) - (Y - 1) * 3 + 1
Z = 4 (K - 1) - X + 1 - 3Y + 3 + 1
So, base on this formula: Z = 4K - X - 3Y + 1