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

for _ in range(int(stdin.readline())):
    l = int(stdin.readline())
    a = list(map(int, stdin.readline().split()))
    maxs = max(a)
    idx = -1
    if a[0] == maxs:
        for i in range(l):
            if a[i] != maxs:
                idx = i
                break
    else:
        for i in range(l):
            if a[i] == maxs:
                idx = i + 1
                break
    print(idx) 