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 i in range(t):
    n = int(input())
    ar = list(map(int, input().split()))
    f = True
    m = max(ar)
    for j in range(n):
        if ar[j] == m:
            if j != 0 and j != n - 1:
                if ar[j - 1] < m or ar[j + 1] < m:
                    print(j + 1)
                    f = False
                    break
            elif j == 0:
                if ar[j + 1] < m:
                    print(j + 1)
                    f = False
                    break
            elif j == n - 1:
                if ar[j - 1] < m:
                    print(j + 1)
                    f = False
                    break
    if f:
        print(-1)

