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())
while t > 0:
    n = int(input())
    nums = list(map(int, input().split()))
    maxVal = nums[0]
    cnt = 0
    for i in range(n):
        if nums[i] == nums[0]:
            cnt += 1
        if maxVal < nums[i]:
            maxVal = nums[i]
    if cnt == n:
        print(-1)
    else:
        for i in range(n):
            if nums[i] != maxVal:
                continue
            if i > 0 and nums[i-1] < maxVal:
                print(i+1)
                break
            if i < n-1 and nums[i+1] < maxVal:
                print(i+1)
                break
    t -= 1
