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())
    a = list(map(int, input().split()))
    b = sorted(a)
    if b[0] == b[-1]:
        print(-1)
    else:
        m = max(a)
        for i in range(len(a)):
            if a[i] == m and (i > 0 and a[i - 1] < m or i < n - 1 and a[i + 1] < m):
                print(i + 1)
                break