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




