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 _ in range(t):
    n = int(input())
    arr = list(map(int, input().split()))
    maximum = max(arr)
    for i in range(n):
        if arr[i] != maximum:
            break
    else:
        print(-1)
        continue
    for i in range(n):
        if arr[i] == maximum:
            if i > 0 and i < n-1:
                if arr[i] > arr[i-1] or arr[i] > arr[i+1]:
                    print(i+1)
                    break
            if i == 0:
                if arr[i] > arr[i+1]:
                    print(i+1)
                    break
            if i == n-1:
                if arr[i] > arr[i-1]:
                    print(i+1)
                    break
    else:
        print(-1)