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


from sys import stdin

tt = int(stdin.readline())

for loop in range(tt):

    n = int(stdin.readline())
    a = list(map(int,stdin.readline().split()))

    M = max(a)
    ans = -1
    for i in range(n):
        if a[i] == M:
            if i != 0 and a[i-1] < a[i]:
                ans = i+1
                break
            if i != n-1 and a[i+1] < a[i]:
                ans = i+1
                break

    print (ans)
    
