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

from math import*

t = int(input())

for _ in range(t):
    n = int(input())
    l = list(map(int, input().split()))
    m = max(*l)
    f = False
    j = 0
    for i in range(1, n-1):
        if l[i] == m and l[i-1] < m or l[i+1] < m:
            j = i
            f = True
            break
    if not f:
        print(-1)
    else:
        print(j + 1)