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
input = stdin.readline

for _ in range(int(input())):
    n = int(input())
    a = [int(x) for x in input().split()]
    t = -1
    m = 0
    for i, e in enumerate(a):
        if e > m:
            if i > 0 and a[i-1]<e:
                t = i+1
                m = e
            if i < n -1 and a[i+1] < e:
                t = i+1
                m = e
    print(t)



