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())
    pir = list(map(int,input().split()))
    biggest = max(pir)
    ans = -1
    for i in range(n):
        if pir[i]== biggest and (pir[i] > pir[max(i-1,0)] or pir[i] > pir[min(i+1,n-1)]):
            ans = i
    if ans != -1:
        print(ans+1)
    else:
        print(ans)
