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 i in range(int(input())):
    n = int(input())
    x = list(map(int,input().split()))
    m = max(x)
    ind = -1
    for i in range(len(x)):
        if x[i] == m and ((i>0 and x[i] > x[i-1]) or (i<n-1 and x[i] > x[i+1])):
            ind = i +1
    
    print(ind)