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())

    lis = list(map(int, input().strip().split()))

    maxs = max(lis)
    flag = 0
    for x in range(n):

        if lis[x] == maxs:

            if x == 0:
                if lis[x+1] < maxs:
                    flag = 1
                    print(x+1)
                    break

            elif 0 < x < n-1:
                if lis[x-1] < maxs or lis[x+1] < maxs:
                    flag = 1
                    print(x+1)
                    break

            elif x == n - 1:

                if lis[x-1] < maxs:
                    flag = 1
                    print(x+1)
                    break
    if flag == 0:
        print("-1")
