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())
for i in range(t):
    n = int(input())
    line = input().strip().split()
    nums = [int(x) for x in line]
    max_ = max(nums)
    min_ = min(nums)
    res = -1
    if max_ != min_ :
        for i in range(n):
            if nums[i] == max_ :
                if (i >= 1 and nums[i] > nums[i-1]) or (i <= n-2 and nums[i] > nums[i+1]):
                    res = i+1
                    break
    print(res)