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 = input()
for r in range(T):
    n = input()
    arr =list(map(int,raw_input().split()))
    ans = -1
    maximum = max(arr)
    for i in range(n):
        if arr[i]==maximum:
            if i>0 and arr[i]>arr[i-1]:
                ans = i+1
                break
            if i<n-1 and arr[i]>arr[i+1]:
                ans = i+1
                break


    print ans
