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)

    res = -1
    for i in range(N):
        if arr[i] != mx: continue
        if i > 0 and arr[i-1]!=mx: res = i+1
        if i < N-1 and arr[i+1]!=mx: res = i+1
    
    print(res)