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>0):
    n = int(input())
    a = list(map (int , input().split(' ')))
    amax = 0
    ok = True
    for i in range(n):
        amax= max (amax, a[i])
    for i in range(n):
        amin = 1000000000
        if(i>0): amin = a[i-1]
        if(i<n-1): amin = min(amin, a[i+1])
        if(a[i]>amin and a[i]== amax):
            print(i+1)
            ok = False
            break
    if(ok==True): print(-1)
    t-=1


