There are ~n~ teams numbered from ~0~ to ~n - 1~ in a tournament; each team is also a node in a *DAG*.
You are given the integer ~n~ and a *0-indexed* 2D integer array ~edges~ of length ~m~ representing the *DAG*, where ~edges[i] = [u_{i}, v_{i}]~ indicates that there is a directed edge from team ~u_{i}~ to team ~v_{i}~ in the graph.
A directed edge from ~a~ to ~b~ in the graph means that team ~a~ is *stronger* than team ~b~ and team ~b~ is *weaker* than team ~a~.
Team ~a~ will be the *champion* of the tournament if there is no team ~b~ that is *stronger* than team ~a~.
Return /the team that will be the *champion* of the tournament if there is a *unique* champion, otherwise, return /~-1~/./
*Notes*
- A *cycle* is a series of nodes ~a_{1}, a_{2}, ..., a_{n}, a_{n+1}~ such that node ~a_{1}~ is the same node as node ~a_{n+1}~, the nodes ~a_{1}, a_{2}, ..., a_{n}~ are distinct, and there is a directed edge from the node ~a_{i}~ to node ~a_{i+1}~ for every ~i~ in the range ~[1, n]~.
- A *DAG* is a directed graph that does not have any *cycle*.
*Example 1:*
#+begin_src
Input: n = 3, edges = [[0,1],[1,2]]
Output: 0
Explanation: Team 1 is weaker than team 0. Team 2 is weaker than team 1. So the champion is team 0.
#+end_src
*Example 2:*
#+begin_src
Input: n = 4, edges = [[0,2],[1,3],[1,2]]
Output: -1
Explanation: Team 2 is weaker than team 0 and team 1. Team 3 is weaker than team 1. But team 1 and team 0 are not weaker than any other teams. So the answer is -1.
#+end_src
*Constraints:*
- ~1 <= n <= 100~
- ~m == edges.length~
- ~0 <= m <= n * (n - 1) / 2~
- ~edges[i].length == 2~
- ~0 <= edge[i][j] <= n - 1~
- ~edges[i][0] != edges[i][1]~
- The input is generated such that if team ~a~ is stronger than team ~b~, team ~b~ is not stronger than team ~a~.
- The input is generated such that if team ~a~ is stronger than team ~b~ and team ~b~ is stronger than team ~c~, then team ~a~ is stronger than team ~c~.
