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

t = int(input())
for z in range(t):
    n = int(input())
    l = list(map(int, input().split()))
    ans = -1
    max_ = max(l)
    check = False
    for i in range(n):
        if(l[i]==max_):
            if((n>i+1>=0 and l[i+1]!=max_) or (n>i-1>=0 and l[i-1]!=max_)):
                check = True
                ans = i+1
                break
    print(ans)





