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

for o in range(int(input())):
    n=int(input())
    s=list(map(int,input().split()))
    a=max(s);p=-1
    for i in range(n):
        if i-1>=0:
            if s[i]==a and s[i-1]<a:
                p=i+1
                break
        if i+1<n:
            if s[i]==a and s[i+1]<a:
                p=i+1
                break
    print(p)














