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 k in range(t):
    n=int(input())
    a=list(map(int,input().split()))
    m=max(a)
    nf=-1
    for i in range(1,len(a)-1):
        if (a[i]==m and a[i]>a[i+1]) or (a[i]==m and a[i]>a[i-1]):
            nf=i+1
            break
    if a[0]==m and a[0]>a[1]:
        nf=1
    elif a[-1]==m and a[-1]>a[-2]:
        nf=len(a)
    print (nf)