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

n = int(input())

for i in range(n):
    l = int(input())
    fish = list(map(int,input().strip().split()))[:l]
    dFish = max(fish)
    dFish_pos = fish.index(max(fish))
    pos = -1
    for i in range(l):
        if (i > 0):
            if (fish[i]>fish[i-1] and fish[i] == dFish):
                pos = i+1
                break
        if (i < l-1):
            if (fish[i]>fish[i+1] and fish[i]==dFish):
                pos = i+1
                break
    print(pos)
