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 q in range(t):
    n = int(input())
    a = list(map(int, input().split()))
    s = max(a)
    w = min(a)
    sid = 0
    wid = 0
    wc = False
    sc = False
    for p in range(n):
        if a[p] == s:
            sid = p
            sc = True
        if a[p] == w:
            wid = p
            wc = True
        if wc and sc:
            break
    if s == w:
        print(-1)
    else:
        ts = sid
        tw = wid
        while ts < tw:
            ts += 1
            if a[ts] == s:
                sid = ts
        while tw < ts:
            tw += 1
            if a[tw] == w:
                wid = tw
        print(sid + 1)