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

if __name__ =="__main__":
    for _ in range(int(input())):
        n=int(input())
        l=list(map(int,input().split()))
        x=max(l)
        ans=-1
        for i in range(n):
            if((i!=0) and (l[i]==x) and (l[i-1]<l[i])):
                ans=i+1
                break
            if((i<n-1) and (l[i]==x) and (l[i+1]<l[i])):
                ans=i+1
                break
        print(ans)