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 tt in range(t):
    n = int(input())
    a = [int(i) for i in input().split()]
    mx = 0
    for i in range(len(a)):
        if mx < a[i]:
            mx = a[i]

    found = 0
    for i in range(len(a)):
        if mx == a[i]:            
            if i - 1 >= 0:
                if a[i - 1] < a[i]:
                    found = 1
            if i + 1 < n:
                if a[i + 1] < a[i]:
                    found = 1
            if found:
                print(i + 1)
                break
    if not found:
        print(-1)
            
