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

def ans(n,arr):
    maxi=-1
    res=-1
    for i in range(n):
        if i-1>=0 and arr[i-1]<arr[i]:
            if arr[i]>maxi:
                maxi=arr[i]
                res=i
        elif i+1<n and arr[i+1]<arr[i]:
            if arr[i]>maxi:
                maxi=arr[i]
                res=i
    return res+1 if res!=-1 else -1

T=int(input())
for i in range(T):
    n=int(input())
    arr=list(map(int,input().strip().split(" ")))
    print(ans(n,arr))
