There are **N **gas stations along a circular route, where the amount of gas at station **i** is **arr[i]**. You have a car with an unlimited gas tank and it costs **cost[i]** of gas to travel from station i to its next station (i+1). You begin the journey with an empty tank at one of the gas stations. Return the **minimum starting gas station’s index** if you can travel around the circuit once, otherwise return -1

**Problem Note**

- Completing the circuit means starting at
**i**and ending up at**i**again. - If there exists a solution, it is guaranteed to be unique.
- Both input arrays are non-empty and have the same length.
- Each element in the input arrays is a non-negative integer.

**Example 1**

```
Input:
arr[] = [1,2,3,4,5]
cost[] = [3,4,5,1,2]
Output: 3
Explanation:
Start at station 3 (index 3) and fill up with 4 unit of gas. Gas available in Tank = 0 + 4 = 4
Travel to station 4.Gas available in tank = 4 - 1 + 5 = 8
Travel to station 0.Gas available in tank = 8 - 2 + 1 = 7
Travel to station 1.Gas available in tank = 7 - 3 + 2 = 6
Travel to station 2.Gas available in tank = 6 - 4 + 3 = 5
Travel to station 3.The cost is 5.Your gas is just enough to travel back to station 3.Therefore, return 3 as the starting index.
```

**Example 2**

```
Input:
arr[] = [2,3,4]
cost[] = [3,4,3]
Output: -1
Explanation:
You can't start at station 0 or 1, as there is not enough gas to travel to the next station.
Let's start at station 2 and fill up with 4 unit of gas. Gas available in tank = 0 + 4 = 4
Travel to station 0.Gas available in tank = 4 - 3 + 2 = 3
Travel to station 1.Gas available in tank = 3 - 3 + 3 = 3
You cannot travel back to station 2, as it requires 4 unit of gas but you only have 3.Therefore, you can't travel around the circuit once no matter where you start.
```