I think his problem has one missing test case.
It doesn’t test for edge cases.
If coins remaining = 16
and covaxine price = 16
and covishield price = 20
So, ideally 16 - 16 >= 0
Therefore ans should be incremented by 1.
But, I used condition 16 - 16 > 0
Therefore my ans didn’t get incremented by 1.
But then also I got AC in all except TLE in 2 subtasks.