1
3
5 3 4
 6
5
5 3 4 4 5
3
1 1 1
5
4 4 3 4 4
5
5 5 4 3 2
3
1 1 2
5
5 4 3 5 5
 1
3
10 1 5

1
 1
-1
2
2
3
1
 1

quant = int(input())
for i in range(0, quant):
    quantity = int(input())
    count = list(map(int, input().split()))
    minimum = min(count)
    maximum = max(count)
    if minimum == maximum:
        print("-1")
    else:
        i = count.index(minimum)
        if count.index(minimum) > count.index(maximum):
            while count[i] != maximum:
                i = i - 1
        else:
            while count[i] != maximum:
                i = i + 1
        print(i+1)