See this thread for the general idea.

Though in this case you will be assing 4 4's and taking away 3 5's. Take

a bit of care to make sure that you have enough 5s to take 3 away.

So suppose you can make n as a sum of 4's and 5's, add 4 4's, then if there

are three or more 5's take 3 5's out, you now have a total of n+1.

If there are no 5's take 5 4's (at this point we have a minimum of 7 of them)and replace with 4 5's, So now the 3 5's can be removed leaving a total of

n+1.

RonL