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 i1 in range(int(input())):
    n=int(input())
    l=list(map(int,input().split()))
    
    c=l.copy()
    c.sort()
    if c[0]==c[-1]:
        print(-1)
    else:
        print(l.index(max(l))+1)