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

n=int(input())
ls=[]
for m in range(n):
    kjkhjh=int(input())
    f=list(map(int,input().split()))
    ls.append(f)
for i in ls:
    x=0
    maxim=max(i)
    for j in range(len(i)):
        if i[j]==maxim:
            if j!=0:
                if i[j] > i[j-1]:
                    print(j+1)
                    x=1
                    break
            if j!=len(i)-1:
                if i[j] > i[j+1]:
                    print(j+1)
                    x=1
                    break
    if x==0:
        print(-1)




