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

m = int(input())
for j in range(m):
    n = int(input())
    arr = [int(x) for x in input().split()]
    allEq = True
    for i in range(n - 1):
        if arr[i] != arr[i + 1]:
            allEq = False
            break
    if allEq:
        print(-1)
        continue
    mx = max(arr)
    for i in range(n):
        if arr[i] != mx:
            continue
        if i != 0 and arr[i - 1] < arr[i]:
            print(i + 1)
            break
        if i != n - 1 and arr[i + 1] < arr[i]:
            print(i + 1)
            break
