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())):
    o=0
    n=int(input())
    l=list(map(int,input().split()))
    if l==[l[0]]*len(l):
        print(-1)
        continue
    else:
        mx=max(l)
        for i in range(1,n-1):
            if l[i]==mx and (l[i]>l[i-1] or l[i]>l[i+1]):
                print(i+1)
                o=1
                break
        if o==1:continue
        if l[0]==mx and l[0]>l[1]:
            print(1)
            continue
        if l[-1]==mx and l[-1]>l[-2]:
            print(len(l))
            continue
