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 q in range(t):
    n=int(input())
    a=[int(z)for z in input().split()]
    m=max(a)
    p=True
    for i in range(n):
        if a[i]==m:
            if i==0:
                if a[i+1]<a[i]:
                    print(i+1)
                    p=False
                    break
            elif i==n-1:
                if a[i-1]<a[i]:
                    print(i+1)
                    p=False
                    break
            else:
                if a[i-1]<a[i] or a[i+1]<a[i]:
                    print(i+1)
                    p=False
                    break
                else:
                    continue
    if p:
        print(-1)
