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

for _ in range(int(input())):
    n = int(input())
    a = list(map(int,input().split()))
    f = len(set(a))==1
    if f:
        print(-1)
        continue
    lst = a[0]
    res = -1
    for i in range(n):
        if a[i]>=lst:
            if (i!=0 and a[i]>a[i-1]) or (i!=n-1 and a[i]>a[i+1]):
                lst = a[i]
                res = i
    print(res+1)
