Codeforces 27B Tournament（dfs，判断有向图中点的连通性)

Tournament
Time Limit:2000MS     Memory Limit:262144KB     64bit IO Format:%I64d
& %I64u
Submit Status

Description

The tournament «Sleepyhead-2010» in the rapid falling asleep has just finished in Berland. n best participants from the country have participated in it. The tournament consists of games, each
of them is a match between two participants. n·(n - 1) / 2 games were played during the tournament, and each participant had a match with each other participant.

The rules of the game are quite simple — the participant who falls asleep first wins. The secretary made a record of each game in the form «xiyi»,
where xi and yi are the numbers of participants. The
first number in each pair is a winner (i.e. xi is a winner and yi is
a loser). There is no draws.

Recently researches form the «Institute Of Sleep» have found that every person is characterized by a value pj — the speed of falling asleep. The person
who has lower speed wins. Every person has its own value pj, constant during the life.

It is known that all participants of the tournament have distinct speeds of falling asleep. Also it was found that the secretary made records about all the games except one. You are to find the result of the missing game.

Input

The first line contains one integer n (3 ≤ n ≤ 50) — the number of participants. The following n·(n - 1) / 2 - 1 lines
contain the results of the games. Each game is described in a single line by two integers xi, yi (1 ≤ xi, yi ≤ n, xi ≠ yi),
where xi и yi are the numbers of the opponents in this
game. It is known that during the tournament each of the n participants played n - 1 games, one game with each other participant.

Output

Output two integers x and y — the missing record. If there are several solutions, output any of them.

Sample Input

Input

4
4 2
4 1
2 3
2 1
3 1

Output

4 3

题意：给出一个完全竞赛图，去掉一条边，让你求出这条边。

思路：先不考虑这条边的方向，求出这条边的两个顶点（u,v），然后从其中一个顶点u深搜，看能否连通道另一个顶点v，如果可以，输出顺序为 u，v。否则相反。

代码如下：