Most people wouldn’t think that it would take rigorous mathematical proof to show how many folds it takes to make a donut shape out of paper. Yet, no one could quite figure it out until recently.

In a new paper, published in Proceedings of the National Academy of Sciences, mathematician Richard Evan Schwartz provides detailed proof of where the line is drawn when it comes to the fewest folds required to construct a torus—the proper name for the shape of a donut—from a piece of paper.