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#include
using namespace std;
int n,m,pic[1100][1100],d[1100],road[1500],now;
void dfs(int x)
{
for(int i=1; i<=500; i++)
{
if(pic[x][i])
{
pic[x][i]--;
pic[i][x]--;
dfs(i);
}
}
road[++now]=x;
}
int main()
{
cin>>m;
for(int i=1; i<=m; i++)
{
int x,y;
cin>>x>>y;
pic[x][y]++;
pic[y][x]++;
d[x]++;
d[y]++;
}
int st=1;
for(int i=1; i<=500; i++)
{
if(d[i]%2)
{
st=i;
break;
}
}
dfs(st);
for(int i=now; i>0; i--)
{
cout<