function [K] = genKey(n)
%GENKEY Generates a random substitution cipher key.
% K = genKey  Generates an n-by-2 table where the first colunmn contains 
%             the numbers 1:n corresponding to the letters of the plaintext
%             alphabet. The 2nd column represents the substituted cipher 
%             alphabet.
%               [1 4]      a --> d
% Example:  K = [2 1]  ==> b --> a     cab --> edb  
%               [3 5]      c --> e

%YOUR CODE BELOW%
