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 _ in range(int(input())):
    n = int(input())
    a = list(map(int, input().split()))

    m = max(a)
    flag = -1
    for i in range(n):
        if a[i] == m:
            if i == 0:
                if a[i+1] < m:
                    print(i+1)
                    flag = 1
                    break
            elif i == n-1:
                if a[i - 1] < m:
                        print(i+1)
                        flag = 1
                        break

            else:
                if a[i + 1] < m or a[i - 1] < m:
                    print(i+1)
                    flag = 1
                    break

    if flag == -1:
        print(-1)