Imo this is very easy

1. Loop through every pump
2. Check if a pump has more petrol than the kilometer (1st condition)
3. Test that pump. If during the tour, the remaining fuel >= 0 (2nd condition)
4. Return index of the pump that passed 2 conditions note: remaining fuel = fuel - distance (kilometer)

The challenge is how to test 2nd condition. If you want to test a pump number 2, than it need to go through [2 > 3 > 4 > 5 > 1] if there is 5 pumps. If during testing and that specific pump's remaining fuel get to below 0 than skip that pump