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)
    for i in range(n):
        if arr[i]==mx:
            if i-1>=0 and arr[i-1]<mx:
                print(i+1)
                break
            if i+1<n and arr[i+1]<mx:
                print(i+1)
                break
    else:
        print(-1)