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())
    arr=list(map(int,input().split()))
    if max(arr)==min(arr):
        print(-1)
    else:    
        li=[]
        for i in range(n):
            li.append([arr[i],i])
        li.sort()
        sort_index=[]
        for x in li:
            sort_index.append(x[1])
        print(sort_index[n-1]+1)    
        