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())
for _ in range(t):
    n=int(input())
    a=list(map(int,input().split()))
    k=a[0]
    flag=0
    for i in range(n):
        if a[i]!=k:
            flag=1
            break
    if flag==0:
        print(-1)
        continue
    t=a[0]
    maxa=t
    maxindex=0
    for i in range(n):
        if a[i]>maxa:
            maxindex=i
            maxa=a[i]
    for i in range(n):
        if a[i]==maxa and i>0 and a[i-1]<maxa:
            print(i+1)
            break
        if a[i]==maxa and i<n-1 and a[i+1]<maxa:
            print(i+1)
            break