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

tc = int(input())
for _ in range(tc):
    n = int(input())
    arr = list(map(int,input().split()))
    x = max(arr)
    y = arr.index(x)
    flag = 0
    if y == 0:
        for i in range(n):
            if arr[i] != x:
                flag = 1
                y = i
                break
        if flag == 1:
            print(y)
        else:
            print(-1)
    else:
        print(y+1)