#include<bits/stdc++.h>
using namespace std;
#define INIT  ios_base :: sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
#define mp make_pair
#define pb push_back
#define ft first
#define sc second
#define ll long long
#define pii pair<int, int>
#define count_bits __builtin_popcount
#define int ll


ifstream fin("ciclueuler.in"); ofstream fout("ciclueuler.out");
#define cin fin
#define cout fout


int n, m;
vector<pii> g[100010];
vector<int> res;
bool v[500010];
int d[100010];



int32_t main(){
INIT
cin>>n>>m;
for(int i=1; i<=m; i++){
    int u, v; cin>>u>>v;
    g[u].pb(mp(v, i) ); g[v].pb(mp(u, i) );
    d[u]++; d[v]++;
}


stack<int> st;
int x=1;

for(int i=1; i<=n; i++){
    if(d[i]>0){
        x=i;
    }
    if(d[i]%2==1){
        cout<<-1; return 0;
    }
}
st.push(x);

while(!st.empty()){
        int t=st.top();
for(;g[t].size()>0;){
    if(!v[g[t].back().sc ] ){
        v[g[t].back().sc ]=true;
        st.push(g[t].back().ft);g[t].pop_back(); goto Next;
    }
    else{
        g[t].pop_back();
    }
}
res.pb(t);
st.pop();
Next:continue;
}

if(res.size()!=(m+1) ){cout<<"-1"; return 0;}
for(int i=0; i<(res.size()-1); i++){
    cout<<res[i]<<" ";
}




return 0;
}