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 T in range(t):
    n = int(input())
    l = list(map(int, input().split()))
    s = set(l)
    nl = list(s)
    nl.sort()
    x = -1
    if len(nl)>1:
        y = nl[-2]
        x = (l.index(y))+1

    if len(nl)==3:
        for i in range(n):
            if l[i]>l[i+1] or l[i]>l[i-1]:
                x = i+1
                break

    print(x)




