#include <iostream.h>
#include <fstream.h>

#define nmax (1005)
#define nmax2 (5005)


ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");

long a[nmax][nmax],n,m,nr,c[nmax];


void euler(long nod)
{long i;
for (i=1;i<=n;i++)
 if (a[nod][i]!=0)
  {a[nod][i]--;
   a[i][nod]--;
   euler(i);
   }

nr++;
c[nr]=nod;
}




int main()
{long i,x,y;

 fin>>n>>m;
 for (i=1;i<=m;i++)
  {fin>>x>>y;
   a[x][y]+=1;
   a[y][x]+=1;
  }

euler(1);

if (nr<m || a[c[nr]][c[1]]) fout<<-1;
else
for (i=1;i<=m;i++)
fout<<c[i]<<" ";

fout.close();
return 0;
}