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 s in[*open(0)][2::2]:
    a = list(map(int,s.split())); m = max(a)
    for i in range(1,len(a)):
        if a[i]>a[i-1] and a[i]==m or a[i]<a[i-1] and a[i-1]==m: print(i+(a[i]==m)); break
    else: print(-1)