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

for _ in range(int(input())):
    n = int(input())
    a = list(map(int, input().split()))

    _max = a[0]
    SAMEF = True
    ans = -1

    for i in range(n):
        if a[i] >= _max:
            _max = a[i]
            SAMEF = False
            if i > 0 and i < (n-1):
                if a[i-1] < a[i] or a[i+1] < a[i]:
                    ans = i+1
            elif i > 0:
                if a[i-1] < a[i]:
                    ans = i+1
            elif i < n-1:
                if a[i+1] < a[i]:
                    ans = i+1

    if SAMEF:
        print(ans)
    else:
        print(ans)