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())
while(t>0):
    n = int(input())
    arr = list(map(int,input().split()))
    maxi = max(arr)
    idx=-1
    for i in range(0,n):
        if arr[i]!=maxi:
            continue
        if(i>0 and arr[i]>arr[i-1]):
            idx=i+1 
        if(i<n-1 and arr[i]>arr[i+1]):
            idx=i+1
    print(idx)
         
    t-=1
