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 _ in range(t):
    n=int(input())
    arr=list(map(int,input().split(' ')))
    m=max(arr)
    ind=-1
    for i in range(n):
        if(arr[i]==m and i+1<n and arr[i]>arr[i+1]):
            ind=i+1
            break
        if(arr[i]==m and i-1>=0 and arr[i]>arr[i-1]):
            ind=i+1
            break
    print(ind)