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