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

for test in range(int(input())):
    n = int(input())
    a = list(map(int,input().split()))
    maxValue = max(a)
    ans = -1
    for i in range(n):
        if a[i] == maxValue and i + 1 < n and a[i] > a[i + 1] :
            ans = i
        if a[i] == maxValue and i - 1 >= 0 and a[i - 1] < a[i] :
            ans = i
    print(-1 if ans == -1 else ans + 1)
