Problem Statement

N players numbered 1 through N will participate in a round-robin tournament.
Specifically, for every pair $(i,j) (1\leq i \lt j \leq N), Player i$ and Player j play a match against each other once, for a total of $\frac{N(N-1)}{2}$ matches.
In every match, one of the players will be a winner and the other will be a loser; there is no draw.
M matches have already ended. In the i-th match, Player W_i won Player L_i.
List all the players who may become the unique winner after the round-robin tournament is completed.
A player is said to be the unique winner if the number of the player's wins is strictly greater than that of any other player.

Input

Input is given from Standard Input in the following format:
N M
W_1 L_1
W_2 L_2
$\vdots$
W_M L_M

Output

Let $A=(A_1,A_2,\dots,A_K) (A_1\lt A_2 \lt \dots \lt A_K)$ be the set of indices of players that may become the unique winner. Print A in the increasing order, with spaces in between.
In other words, print in the following format.
$A_1 A_2 \dots A_K$

Constraints

• $2\leq N \leq 50$
• $0\leq M \leq \frac{N(N-1)}{2}$
• $1\leq W_i,L_i\leq N$
• $W_i \neq L_i$
• If $i\neq j$, then $(W_i,L_i) \neq (W_j,L_j)$.
• $(W_i,L_i) \neq (L_j,W_j)$
• All values in input are integers.

Sample Input 1

4 2
2 1
2 3

Sample Output 1

2 4

Players 2 and 4 may become the unique winner, while Players 1 and 3 cannot.
Note that output like 4 2 is considered to be incorrect.

Sample Input 2

3 3
1 2
2 3
3 1

Sample Output 2

It is possible that no player can become the unique winner.

Sample Input 3

7 9
6 5
1 2
3 4
5 3
6 2
1 5
3 2
6 4
1 4

Sample Output 3

1 3 6 7

见题面 Input 部分

见题面 Output 部分