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()))
    b=[]
    index=0
    m=a[0] if a[0]>a[1] else -1
    for i in range(1,n-1):
        if (a[i]>a[i-1] or a[i]>a[i+1]) and a[i]>m:
            index=i
            m=a[i]
    if a[n-1]>m and a[n-1]>a[n-2]:
        m=a[n-1]
        index=n-1
    print(index+1 if m>=0 else -1)
