#include <stdio.h>
#include <vector>
#include <algorithm>

using namespace std;
FILE *f=fopen("ciclueuler.in","r");
FILE *g=fopen("ciclueuler.out","w");

vector <int> a[100005],sol;
int s[500005],x,y,n,m,u,i;

int verif(){
int i;

for(i=1;i<=n;i++)
if (a[i].size()%2 == 1 )return 0;

return 1;

}

void dfs(int k){
vector <int>::iterator it;

s[++u]=k;
while (u){
 x=s[u];

 if (a[x].size()){
  y=a[x].back();
  a[x].pop_back();
  s[++u]=y;
  a[y].erase(find(a[y].begin(),a[y].end(),x));
 }
 else{
  sol.push_back(s[u]);
  u--;
 }
}

}


int main()
{
fscanf(f,"%d%d",&n,&m);
for(i=1;i<=m;i++)
{
 fscanf(f,"%d%d",&x,&y);
 a[x].push_back(y);
 a[y].push_back(x);
}

if (!verif())fprintf(g,"%d",-1);
else {
dfs(1);
for(i=0;i<=sol.size()-2;i++)
fprintf(g,"%d ",sol[i]);

}


fclose(g);
return 0;
}