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())):
    input()
    seq = list(map(int,input().split()))
    if max(seq) != min(seq):
        dom = max(seq)
        for (i,x) in enumerate(seq):
            if x == dom and ((i+1 < len(seq) and seq[i+1] < x) or (i-1 >= 0 and seq[i-1] < x)):
                print(i+1)
                break
    else:
        print(-1)
