#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cctype>
#include <cmath>
#include <string>
#include <algorithm>
#include <vector>
#include <queue>
#include <deque>
#include <set>
#include <stack>
#include <ctime>
#include <cassert>
using namespace std;

#define PRO "ciclueuler"
void OpenFiles(int EVAL)
{
	if(EVAL)
	{
		char input[100] = PRO, output[100] = PRO;
		freopen(strcat(input, ".in"),"r",stdin);
		freopen(strcat(output,".out"),"w",stdout);
	} else
	{
		freopen("test.in","r",stdin);
		freopen("test.out","w",stdout);
	}
}

#define MAX 100001
#define MOD 666013
#define INF 0xffffff
#define EPS 1E-8

int n,m,nr_m;
vector<pair<int,int> >graf[MAX];
vector<int>ciclu;
stack<int>st;

void euler(int x)
{
	st.push(x);
	while(st.size() > 0)
	{
		go_in:
		x = st.top();
		for(int i=0;i<graf[x].size();i++)
		if(graf[x][i].second == 1)
		{
			nr_m++;
			graf[x][i].second = 0;
			st.push( graf[x][i].first );
			goto go_in;
		}
		ciclu.push_back(st.top());
		st.pop();
	}
}

bool eulerian()
{
	if(nr_m == m)return 1;
	for(int i=0, x = ciclu[ciclu.size()-1];i< graf[x].size();i++)
		if(graf[x][i].first == ciclu[0])return 1;
	return 0;
}

int main(int argv,char *args[])
{	
OpenFiles(argv==0);
	/* start code */
	scanf("%d %d",&n,&m);
	for(int i=1,x,y;i<=m;i++)
	{
		scanf("%d %d",&x,&y);
		graf[x].push_back(make_pair(y,1));
	}
	euler(1);
	if(nr_m < m) printf("-1\n");else
	for(int i=ciclu.size()-1;i>=0;i--)
		printf("%d ",ciclu[i]);
	/* end */
	return 0;
}