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

testCases = int(input())
while testCases > 0:
    n = int(input())
    a = input().split()
    max = -1
    for i in range(n):
        a[i] = int(a[i])
        if a[i] > max:
            max = a[i]
    domPiranhaPos = -2
    for i in range(n):
        if a[i] == max:
            if i > 0 and a[i] > a[i - 1]:
                domPiranhaPos = i
                break
            elif i < n - 1 and a[i] > a[i + 1]:
                domPiranhaPos = i
                break
    print (domPiranhaPos + 1)
    testCases -= 1