Gas Station Tour Problem

You are presented with a circular track consisting of several petrol pumps. Each petrol pump is indexed from 0 to N-1 and offers certain attributes:

• The quantity of petrol available at the pump.
• The distance to the subsequent petrol pump.

Your objective is to determine the first petrol pump from which a truck, with an empty but unlimited fuel tank, can start its journey and complete the circle or establish that a full circle is not possible.

Note that the truck pauses at every pump, refuels, and consumes 1 litre of petrol per kilometre traveled.

Example:

Input:

3
4
4 6
6 5
7 3
4 5
3
6 4
5 3
8 6
2
2 3
2 2

Output:

1
0
-1

Constraints:

• 1 ≤ T ≤ 50
• 1 ≤ N ≤ 10⁵
• 1 ≤ Amount of petrol on each pump ≤ 10⁹
• 1 ≤ Distance to next pump ≤ 10⁹

Note: You are to implement only the function as the output procedures are handled. Ensure that the indices in your results are 0-based.