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

t = int(input())
a = 0
v = 0
for i in range(t):
    a = int(input())
    line = list(map(int, input().split()))
    v = line.index(max(line))
    if len(set(line)) == 1:
        print('-1')
        continue
    while True:

        if v >= 0 and v <= len(line):

            if line[v] > line[v-1] or line[v] > line[v+1]:

                print(v)
                break
            else:
                v += 1
