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

n = int(input())
for i in range(n):
    flag = 0
    k = int(input())
    al = list(map(int,input().split()))
    p = max(al)
    ans = []
    for i in range(len(al)):
        if al[i] == p:
            ans.append(i)
    for i in ans:
        if i == 0:
            if al[1]<al[0]:
                print(1)
                flag = 1
                break
        elif i == len(al)-1:
            if al[i]>al[i-1]:
                print(len(al))
                flag = 1
                break
        else:
            if al[i] > al[i-1] or al[i] >al[i+1]:
                print(i+1)
                flag = 1
                break
    if flag == 0:
        print(-1)