#include <fstream>
#include <vector>
#define MMAX 500002
#define NMAX 100002
using namespace std;
ifstream fin ("ciclueuler.in");
ofstream fout ("ciclueuler.out");
int n, m;
struct muchie {
    int x, y;
    bool uz;
};
muchie LM[MMAX];
int S[MMAX];
int vf;
vector<int>sol;
vector<int>LA[NMAX];

void citire();
bool verificare();
void euler();
void afisare();

int main()
{
    citire();
    if (verificare())
        fout << -1;
        else
        {euler();
         afisare();}
 fout.close();
}

void citire()
{int i, x, y;
 fin >> n >> m;
 for (i=1; i<=m; i++)
      {
       fin >> x >> y;
       LA[x].push_back(i);
       LA[y].push_back(i);
       LM[i].x=x; LM[i].y=y; LM[i].uz=0;
      }
}
bool verificare(){
 int i;
 for (i = 1; i<=n; i++)
     if (LA[i].size()%2)
       return 1;
return 0;
}

void euler()
{int urm_muchie, crt;
 S[1]=1; vf=1;
 while (vf>0)
       { crt = S[vf];
        if (LA[crt].size()==0)
            { sol.push_back(crt);  vf--;  }
            else
            {
            urm_muchie = LA[crt].back();
            LA[crt].pop_back();
            if (LM[urm_muchie].uz == 0)
                {LM[urm_muchie].uz = 1;
                 if (crt == LM[urm_muchie].x)
                     S[++vf]=LM[urm_muchie].y;
                     else
                     S[++vf]=LM[urm_muchie].x;
                }
         }
    }
}
void afisare()
{int i;
 for (i = 0; i<sol.size()-1; i++)
     fout<< sol[i]<< ' ';
}