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 t in range(int(input())):
    n=int(input())
    a=list(map(int,input().split()))
    mini=99999999999
    maxi=-1
    store=0
    a=[a[0]]+a+[a[-1]]
    for i in range(1,n+1):
        if(a[i-1]<a[i] or a[i]>a[i+1]):
            if(a[i]>maxi):
                maxi=a[i]
                store=i
    for i in range(n):
        mini=min(mini,a[i])
    if(maxi==-1):
        print(-1)
    else:
        print(store)