doesn't "5ab" have a number of variables greater than "-c"?
Maybe you're misunderstanding the instructions. Each letter is a variable, you must sort by the "number of variables", not by the coefficient

One of the test cases is looking for -c+5ab but the instructions say:

All monomials appears in order of increasing number of variables, e.g.:
"-abc+3a+2ac" -> "3a+2ac-abc", "xyz-xz" -> "-xz+xyz"

the code should return -1 when any of the 3 conditions are not met. The if statement is the check to see if bounce is between 0 and 1 and the while loop checks to see if the window is above 0 and the height at which the ball being dropped is higher than the window. If any of these aren't true then it will skip the if statement and therefore the while loop and return -1.

Confession time. This was basically my solution, however my logic says seen should start at 1 (as it will bounce down once and not come up again or forfeight and return -1), my test results were all coming back 2 more than the answer, so I changed seen to -1 and tested it to see if it would work with ALL the tests aaand it did. But I don't understand why... if someone could share some insight with me I would appreciate it very much