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

def chkList(lst):
    return len(set(lst)) == 1
t=int(input())
for _ in range(t):
    n=int(input())
    a=list(map(int,input().split()))
    m=max(a)
    flag=True
    flag1=False
    if(chkList(a)):
        print(-1)
        flag=False
    if flag:
        for i in range(len(a)):
            if a[i] == m:
                if ((i - 1 >= 0) and (a[i - 1] < a[i])) or ((i + 1 < len(a)) and (a[i + 1] < a[i])):
                    print(i+1)
                    flag1= True
                    break

        if(flag1==False):
          print(-1)









