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 j in range(t):
    n = int(input())
    a = input().split()
    for i in range(len(a)):
        a[i]=int(a[i])


    maximum = (max(a))
    flag=0
    n = len(a)
    if(a[0]==maximum):
        if(a[1]<maximum):
            flag=1
            print(1)

    elif(a[n-1]==maximum):
        if(a[n-2]<maximum):
            flag=1
            print(n)

    if(flag==0):
        for i in range(1,n-1):
            if(a[i]==maximum):
                if(a[i+1]<maximum or a[i-1]<maximum):
                    flag=1
                    print(i + 1)
                    break
    if(flag==0):
        print('-1')