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 _ in range(int(input())):
    n=int(input())
    a=list(map(int,input().split()))
    m=max(a)
    index=[]
    for i,n in enumerate(a):
        if n==m:
            index.append(i)
    flag=False
    for i in index:
        if (i-1>=0 and a[i-1]<m) or (i+1<len(a) and a[i+1]<m):
            #print('here')
            flag=True
            ans=i
            break
    #print(index,n)
    if flag:
        print(ans+1)
    else:
        print(-1)
