#include <bits/stdc++.h>
using namespace std;
ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");

#define mp make_pair
#define f first
#define s second

int n, m, x, y, i, crt;
int grad[ 100010 ], it[ 100010 ];
bool viz[ 100010 ], used[ 500010 ];
vector<pair<int, int> > graf[ 100010 ];
stack<int> S;

bool isEuler() {
    S.push( 1 );
    while ( !S.empty() ) {
        crt = S.top();
        viz[ crt ] = true;
        for ( it[ crt ] ; it[ crt ] < graf[ crt ].size() ; it[ crt ]++ ) {
            if ( !viz[ graf[ crt ][ it[ crt ] ].f ] ) {
                S.push( graf[ crt ][ it[ crt ] ].f );
                break;
            }
        }
        if ( it[ crt ] == graf[ crt ].size() ) {
            S.pop();
        }
    }

    for ( i = 1 ; i <= n ; i++ ) {
        if ( !viz[ i ] || grad[ i ] % 2 || grad[ i ] == 0 )
            return false;
        it[ i ] = 0;
    }

    return true;
}

int main()
{
    fin >> n >> m;
    for ( i = 1 ; i <= m ; i++ ) {
        fin >> x >> y;
        graf[ x ].push_back( mp( y , i ) );
        graf[ y ].push_back( mp( x , i ) );
        grad[ x ]++; grad[ y ]++;
    }

    if ( isEuler() ) {
        S.push( 1 );
        while ( !S.empty() ) {
            crt = S.top();
            for ( it[ crt ] ; it[ crt ] < graf[ crt ].size() ; it[ crt ]++ ) {
                if ( !used[ graf[ crt ][ it[ crt ] ].s ] ) {
                    used[ graf[ crt ][ it[ crt ] ].s ] = true;
                    S.push( graf[ crt ][ it[ crt ] ].f  );
                    break;
                }
            }
            if ( it[ crt ] == graf[ crt ].size() ) {
                if ( S.size() > 1 )
                    fout << S.top() << ' ';
                S.pop();
            }
        }
    } else {
        fout << -1;
    }

}