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())):
    n=int(input())
    nn=[int(s) for s in input().split()]
    r=max(nn)
    if nn.count(r)==1:
        print(nn.index(r)+1)
    else:
        kek=-1
        for k in range(n):
            if nn[k]==r:
                if k-1>=0:
                    if nn[k-1]!=r:
                        kek=k+1
                        break
                if k+1<n:
                    if nn[k+1]!=r:
                        kek=k+1
                        break
        print(kek)