#include <stdio.h>
#define MAXN 100000
#define MAXM 500000
#define BUFF (1 << 20)
FILE *in;
int ult[MAXN], deg[MAXN], nod[2 * MAXM], next[2 * MAXM];
int st[MAXM + 1], d = 0;
int rez[MAXM + 1], drez;
char fol[MAXM];
char buff[BUFF];
int p = BUFF;

inline char cif(char ch){
  if(ch >= '0' && ch <= '9')
    return 1;
  return 0;
}

inline char getch(){
  if(p == BUFF){
    fread(buff, 1, BUFF, in);
    p = 0;
  }
  p++;
  return buff[p - 1];
}

inline int getnum(){
  char ch = getch();
  while(!cif(ch))
    ch = getch();
  int rez = 0;
  while(cif(ch)){
    rez *= 10;
    rez += ch - '0';
    ch = getch();
  }
  return rez;
}

inline void ceuler(int x){
  st[d] = x;
  d++;
  while(d > 0){
    if(ult[st[d - 1]] == -1){
      rez[drez] = st[d - 1];
      drez++;
      d--;
    }
    else  if(fol[ult[st[d - 1]] / 2])
      ult[st[d - 1]] = next[ult[st[d - 1]]];
    else{
      fol[ult[st[d - 1]] / 2] = 1;
      st[d] = nod[ult[st[d - 1]]];
      ult[st[d - 1]] = next[ult[st[d - 1]]];
      d++;
    }
  }
}

int main(){
  in = fopen("ciclueuler.in", "r");
  int n, m, i, x, y, dr = 0;
  n = getnum();  m = getnum();
  for(i = 0; i < n; i++)
    ult[i] = -1;
  for(i = 0; i < m; i++){
    x = getnum();  y = getnum();
    x--;  y--;
    deg[x]++;
    nod[dr] = x;
    next[dr] = ult[y];
    ult[y] = dr;
    dr++;

    deg[y]++;
    nod[dr] = y;
    next[dr] = ult[x];
    ult[x] = dr;
    dr++;
  }
  fclose(in);
  FILE *out = fopen("ciclueuler.out", "w");
  char g = 0;
  for(i = 0; i < n; i++){
    if(deg[i] & 1)
      g = 1;
  }
  if(!g){
    ceuler(0);
    for(i = 0; i < drez - 1; i++)
      fprintf(out, "%d ", rez[i] + 1);
  }
  else
    fprintf(out, "-1");
  return 0;
}