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 ct in range(int(input())):
    n = int(input())
    v = [int(i) for i in input().split()]

    ma = max(v)

    for i in range(n):
        if v[i] == ma:
            if (i > 0 and v[i-1] < ma) or (i < n-1 and v[i+1] < ma):
                print(i+1)
                break
    else:
        print(-1)