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 i in range(t):
    n=int(input())
    arr=list(map(int,input().split()))
    #print(arr)
    m=max(arr)
    found=False
    for i in range(n):
        if arr[i]<m:
            found=True
            break
    for i in range(n):
        if arr[i]!=m:
            if i+1<n and arr[i+1]==m :
                print(i+2)
                break
            elif i-1>=0 and arr[i-1]==m:
                print(i)
                break
    if not found:
        print(-1)