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 t in range(int(input())):
    input()
    arr = list(map(int,input().split()))
    ans = -1
    mx = max(arr)

    for i in range(len(arr)):
        if arr[i] == mx and ((i-1 >=0 and arr[i-1] < mx) or (i + 1 < len(arr) and arr[i+1] < mx)):
            ans = i + 1

    print(ans)

