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

from collections import Counter
for _ in range(int(input())):
    n=int(input())
    l=list(map(int,input().split()))
    j=l.index(max(l))
    c=0
    for i in range(1,n-1):
        if l[i]==l[j] and ( l[i-1]<l[i] or l[i+1]<l[i]):
            print(i+1)
            c=1
            break
    if c==0:
        if l[j]==l[0] and l[0]>l[1]:
            print(1)
        elif l[j]==l[-1] and l[-1]>l[-2]:
            print(n)
        else:
            print(-1)
            
