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 = [int(i) for i in input().split()]
    maximum = max(a)
    minimum = min(a)
    if maximum == minimum:
        print(-1)
    else:
        for ind in range(n):
            if ind == 0:
                if a[ind] > a[ind + 1] and a[ind] == maximum:
                    print(ind + 1)
                    break
            elif ind == n - 1:
                if a[ind] > a[ind - 1] and a[ind] == maximum:
                    print(ind + 1)
                    break
            else:
                if (a[ind] > a[ind - 1] or a[ind] > a[ind + 1]) and a[ind] == maximum:
                    print(ind + 1)
                    break
