Did you get the answer? I am looking for the same thing. Katas this kata and another kyu3 kata doesn't react. Do you have the left window outlined in red?

I passed sample tests. For random it says I passed 1 and failed 0. The left window is outluned in red and the arrow in front of random tests is red. What is the problem? Is it not optimal enough? Did I fail randoms but it just doesnt show? Works with every case I test myself. Using C++