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 _ in range(T):
    n=int(input())
    arr=list(map(int,input().split()))
    ch=arr.copy()
    ch.sort()
    mx=ch[-1]
    if ch.count(mx)==n:
        print(-1)
    else:
        ind=-1
        for i in range(n):
            if arr[i]==mx:
                if i-1>=0:
                    if arr[i-1]<mx:
                        ind=i+1
                        break
                if i+1<n:
                    if arr[i+1]<mx:
                        ind=i+1
                        break
        print(ind)
                    
                    
                    
