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