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

        print(ans+1)
