Yup... thanks!

I was 24 hours awake before and didn't realize. Thanks by the way :)

I failed on some random tests like this, because I think there's something wrong.
Line = 25,25,25,100,25,25,25,100,25,25,25,100,25,50,25,100,25,25,50,100 - Expected: 'YES', instead got: 'NO'
(25,25,25) I get 100, then use the three 25 for change. Same thing twice. So I get 300.
+25, I get 50, then use the 25 for change. No 25's left, then I get 25. Someone pays 100. I would be able to give change, so 'NO'