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()))
    mx = max(a)
    ans = None
    for i in range(n):
        if mx == a[i]:
            if i - 1 >= 0 and mx != a[i - 1]:
                ans = i
                break
            if i + 1 < n and mx != a[i + 1]:
                ans = i
                break
    if ans is None:
        print(-1)
    else:
        print(ans+1)
