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 z in range(t):
    n=int(input())
    a=list(map(int, input().split()))
    x=max(a)
    ans=-2
    if a[0]==x and a[0]>a[1]:
        print(1)
    elif a[n-1]==x and a[n-1]>a[n-2]:
        print(n)
    else:
        for i in range(1, n-1):
            if a[i]==x and (a[i]>a[i-1] or a[i]>a[i+1]):
                ans=i
                break
        print(ans+1)