Four people are in a bar.
Ben owes Glen a drink. Glen owes Rhen two drinks. Rhen owes Sven three drinks. Sven owes Ben four drinks.
To settle up, what is the minimum number of drinks that need to be bought by who for whom?
We have from the problem, Ben owes Glen one drink, Glen owes Rhen two drinks, Rhen owes Sven three drinks and Sven owes Ben four drinks.
So, we can calculate that finally, someone owes Ben three drinks and each of the others (i.e., Glen, Rhen and Sven) all owe someone one drink each. So, to settle up, each of Glen, Rhen and Sven buy a drink for Ben.
That’s it, which I believe is the correct solution.