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(input()):
    n=input()
    a=map(int,raw_input().split())
    lar=max(a)
    pos=-1
    for i in range(n):
        if a[i]==lar:
            if i==0:
                if a[i]>a[i+1]:
                    pos=i+1
                    break
            elif i==n-1:
                if a[i]>a[i-1]:
                    pos=i+1
                    break
            else:
                if a[i]>a[i-1] or a[i]>a[i+1]:
                    pos=i+1
                    break
    print pos
