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

t = int(input())
for z in range(t):
    n = int(input())
    arr = list(map(int,input().split()))
    flag = False
    maxi = max(arr)
    for i in range(len(arr)):
        if(arr[i]==maxi):
            if(i-1 >=0 and arr[i-1]<arr[i]):
                res = i
                flag = True
                break
            if(i+1 < n and arr[i+1]<arr[i]):
                res = i
                flag = True
                break
    if(flag):
        print(res+1)
    else:
        print('-1')