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())
    l = list(map(int, input().split()))
    if len(set(l)) == 1:
        print(-1)
    else:
        mx = max(l)
        for i in range(n):
            if l[i] == mx:
                if (i < n - 1 and l[i] > l[i + 1]) or (i > 0 and l[i] > l[i - 1]):
                    print(i + 1)
                    break
