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):
    ff = 0
    n = int(input())
    a = [int(x) for x in input().split()]
    m = max(*a)
    for j in range(n):
        if a[j] == m:
            if j != n - 1 and j != 0:
                if a[j+1] < a[j] or a[j-1] < a[j]:
                    print(j+1)
                    ff = 1
                    break
            elif j == n - 1:
                if a[j-1] < a[j]:
                    print(j+1)
                    ff = 1
                    break
            else:
                if a[j+1] < a[j]:
                    print(j+1)
                    ff = 1
                    break
    if ff == 0:
        print(-1)
