Suppose there is a circle. There are n petrol pumps on that circle. You will be given two sets of data.

**1.** The amount of petrol that every petrol pump has.

**2.** Distance from that petrol pump to the next petrol pump.

Your task is to complete the function **tour** which returns an integer denoting the first point from where a truck will be able to complete the circle (The truck will stop at each petrol pump and it has infinite capacity).

**Note :** Assume for 1 litre petrol, the truck can go 1 unit of distance.

**Input**

The first line of input will be the no of test cases . Then T test cases follow . Each Test case contains 2 lines . The first line will contain an integer N denoting the no of petrol pumps and in the next line are N space separated values **petrol** and **distance** denoting the amount of petrol every petrol pump has and the distance to next petrol pump respectively .

**Output**

The output of each test case will be the index of the the first point from where a truck will be able to complete the circle otherwise -1 .

**Constraints:**

1<=T<=100

1<=N<=50

1<=petrol,distance<=100

**Example (To be used only for expected output)
Input**

1

4

4 6 6 5 7 3 4 5

1

Above there are 4 petrol pumps with amount of petrol and distance to next petrol pump value pairs as {4, 6}, {6, 5}, {7, 3} and {4, 5}. The first point from where truck can make a circular tour is 2nd petrol pump. Output in this case is 1 (index of 2nd petrol pump).