Why it works
		¡ In this example, A was the most common letter ¡ In ABRACADABRA: l 5 As   code for A is 1 bit long l 2 Rs   code for R is 2 bits long l 2 Bs   code for B is 3 bits long l 1 C   code for C is 4 bits long l 1 D   code for D is 4 bits long