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

cases = int(input())
while cases:
    cases -= 1
    num = int(input())
    arr = list(map(int, input().split()))

    mn = min(arr)
    mx = max(arr)

    if mn == mx:
        print(-1)
    else:
        count = 0
        rem= 0
        strt = False
        printed = False
        first = False
        for i, n in enumerate(arr, start=1):
            if n == mx:
                strt = True
                if not first:
                    first = True
                    rem = i
            else:
                if strt:
                    print(i-1)
                    printed = True
                    break
        if not printed:
            print(rem)
