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

#sily#872
for _ in range(int(input())):
    n=int(input())
    a=[int(x)for x in input().split()]
    cnt=0
    m=0
    ss=-1
    for i in range(n):
        if(a[i]>m):
            m=a[i]
        if(a[i]==m):
            if(i>0 and a[i-1]<a[i]):
                ss=i
            elif(i<n-1 and a[i]>a[i+1]):
                ss=i
    if(ss+1):
        print(ss+1)
    else:
        print(-1)
