How can you design 4-to-16 decoder with five 2-to-4 decoder?

It turned out to be very easy))) But I was thinking for a while to solve the problem... )))
Ok. Lets say we have inputs S3..S0. Let S3 and S2 go to inputs of each of FOUR of decoders; and S1 with S0 go to the inputs of the FIFTH decoder. The four outputs of the FIFTH decoder go to enable lines of the four decoders. Voila! It might be confusing, but just draw the whole thing and you'll see. Now you just need to enable the fifth decoder... HA-HA!