#include <cstdio>
using namespace std;

int n,una,tarnum[2001],tar[2001][2001];
bool found;

void find()
{
	int i,tail=0,head=0,que[2001]={1};
	bool used[2001]={0,1};
	found=false;
	while (!found&&tail<=head)
	{
		for (i=0;i<tarnum[que[tail]];i++)
			if (!used[tar[que[tail]][i]]&&tar[que[tail]][i]!=una)
			{
				if (tar[que[tail]][i]==n)
				{
					found=true;
					break;
				}
				else
				{
					que[++head]=tar[que[tail]][i];
					used[tar[que[tail]][i]]=true;
				}
			}
		tail++;
	}
}

int main(void)
{
	freopen("running.in","r",stdin);
	freopen("running.out","w",stdout);
	int i,e,x,y,recnum=0,rec[2001];
	scanf("%d%d",&n,&e);
	for (i=1;i<=e;i++)
	{
		scanf("%d%d",&x,&y);
		tar[x][tarnum[x]++]=y;
		tar[y][tarnum[y]++]=x;
	}
	for (una=2;una<n;una++)
	{
		find();
		if (!found)
			rec[recnum++]=una;
	}
	printf("%d\n",recnum);
	x=0;
	for (i=0;i<recnum;i++)
	{
		if (x)
			printf(" ");
		else
			x=1;
		printf("%d",rec[i]);
	}
	printf("\n");
	return(0);
}