There is a bus moving in the city, and it takes and drops some people in each bus stop.
You are provided with an array of "bus stops". Each "bus stop" is itself an array containing 2 items:
- the number of people who get on bus at that bus stop
- the number of people who get off the bus at that bus stop
For example, [2, 5]
means that 2 people got on the bus, and 5 people got off the bus at that stop.