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()))
    m=max(a)
    an=-1
    for j in range(n):
        if a[j]==m:
            if j>=1 and j<=n-2:
                if a[j]>a[j-1] or a[j]>a[j+1]:
                    an=j+1
                    break
            elif j==0:
                if a[1]<a[0]:
                    an=j+1
                    break
            else:
                if a[n-2]<a[n-1]:
                    an=j+1
                    break
    print(an) 