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

from pprint import pprint
def do():
    n = int(input())
    dat = list(map(int, input().split()))
    ma = max(dat)
    res = -1
    for i in range(n):
        if dat[i] != ma:
            continue
        if i != 0:
            if ma > dat[i-1]:
                res = i+1
                break
        if i != (n-1):
            if ma > dat[i + 1]:
                res = i+1
                break
    print(res)


q = int(input())
for _ in range(q):
    do()
