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

"""
Author: Q.E.D
Time: 2020-10-20 09:58:20
"""
T = int(input())
for _ in range(T):
    n = int(input())
    a = list(map(int, input().split()))
    m = max(a)
    ans = -1
    for i, x in enumerate(a):
        if (x == m) and ((i > 0 and x > a[i - 1]) or (i < n - 1 and x > a[i + 1])):
            ans = i + 1
            break
    print(ans)
