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())
while t:
    t-=1
    res = -1
    n = int(input())
    l = list(map(int,input().split()))
    m = max(l)
    if(l[0]==m and l[1]<m):
        print(1)
    elif(l[-1]==m and l[-2]<m):
        print(n)
    else:
        for i in range(1,n-1):
            if(l[i]==m and (l[i+1]<m or l[i-1]<m)):
                res = i+1
                break
        print(res)