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 j in range(t):
    n = int(input())

    d = str(input()).split(" ")
    arr = []
    for i in  range(n):
        try:
            arr.append(int(d[i]))
        except:
            pass

    
    mx = max(arr)
    vis = 0
    for i in range(n):
        if arr[i] == mx:
            try:
                if arr[i-1] < mx and i-1>=0:
                    print(i+1)
                    vis = 1
                    break
                if arr[i+1] < mx and i+1<n:
                    print(i+1)
                    vis = 1
                    break
            except:
                pass
    if vis == 0:
        print("-1")
