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 k in range(int(input())):
    n = int(input())
    vec = list(map(int, input().split()))
    m = max(vec)
    ind = -1
    for i in range(0, n):
        if vec[i] == m:
            if i != 0 and vec[i - 1] != m:
                ind = i + 1
                break
            elif i != n - 1 and vec[i + 1] != m:
                ind = i + 1
                break
    print(ind)