#include <bits/stdc++.h>
#define buff_size (1<<17)
char buff[buff_size];
int pos=0;
char outBuff[buff_size];
int outPtr;
using namespace std;
int n,m;
vector <int>  G[500005],sol;
stack  <int>  ST;

FILE*f=freopen("ciclueuler.in","r",stdin);
FILE*g=freopen("ciclueuler.out","w",stdout);

inline void read(int &nr)
{
    while(!isdigit(buff[pos])) if(++pos == buff_size) fread(buff,  1,buff_size, stdin), pos = 0;
    nr = 0;
    while(isdigit(buff[pos]))
    {
        nr = (nr<<1)+(nr<<3)+ buff[pos] - 48;
        if(++pos == buff_size) fread(buff, 1, buff_size, stdin), pos = 0;
    }
}

void read_data()
{   int x,y;
    read(n);read(m);
    for(int i=1;i<=m;i++)
    {
        read(x);read(y);
        G[x].push_back(y);
        G[y].push_back(x);
    }
}

void euler()
{
    for(int i=1;i<=n;i++)  if(G[i].size()%2!=0)  return;

    ST.push(1);
    while(!ST.empty())
    {
        int nod=ST.top();
        if(G[nod].size())
        {
            int vnod=G[nod][0];
            G[nod].erase(G[nod].begin());
            G[vnod].erase(find(G[vnod].begin(),G[vnod].end(),nod));
            ST.push(vnod);
        }

        else  ST.pop(),sol.push_back(nod);
    }
}

inline void putChar(const char &C) {
    outBuff[outPtr++] = C;
    if (outPtr == buff_size) {
        fwrite(outBuff, 1, buff_size, stdout);
        outPtr = 0;
    }
}

inline  void write(int X) {
    static char digs[10];
    int n = 0, q;
    do {
        q = X / 10;
        digs[n++] = X - (q << 1) - (q << 3) + 48;

        X = q;
    } while (X);
    while (n--) {
        putChar(digs[n]);
    }

}

void write_data()
{
    for(int i=0;i<sol.size();i++) write(sol[i]),putChar(' ');
    if(sol.size()==0) putChar('-'),putChar('1');
    fwrite(outBuff, 1, buff_size, stdout);
}

int main()
{
    read_data();
    euler();
    write_data();
}