public static HashMap<Character,Character> rotateMapping(char[] alphabet, int rot)
	{
		HashMap<Character, Character> mapping = new HashMap<Character, Character>();
		for(int i = 0; i < alphabet.length; i++)
		{
			int x = i+ rot;
			while(alphabet.length<=x)
				x -= alphabet.length;
			while(x<0)
				x += alphabet.length;
			mapping.put(alphabet[i], alphabet[x]);
			
		}
		return mapping;
	}