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 i in range(t):
    n=int(input())
    a=[int(x) for x in input().split()]
    req=max(a)
    cnt=0
    ind=-1
    for i in range(n):
        if (a[i]==req):
            cnt+=1
            ind=i
    if (cnt==n): print(-1)
    else: print(ind+1) 
