#include <bits/stdc++.h>
using namespace std;
const int N = 10000000 + 5;

set< pair< int, int > > st;

int to[ N << 1 ], nxt[ N << 1 ], hd[ N ];
bool vis[ N ];
int from[ N ], qu[ N ], deg[ N ], sd[ N ];

int main() {
    ios_base::sync_with_stdio( false );
    cin.tie( nullptr );

    memset( hd, -1, sizeof( hd ) );
    int n, m; cin >> n >> m;

    // 特判無解
    if ( m == 0 ) {
        cout << -1 << '\n';
        return 0;
    }

    // 讀入所有的邊
    for ( int i = 0 ; i < m ; ++ i ) {
        int u, v; cin >> u >> v;
        nxt[ i * 2 ] = hd[ u ];
        to[ i * 2 ] = v;
        hd[ u ] = i * 2;

        nxt[ i * 2 + 1 ] = hd[ v ];
        to[ i * 2 + 1 ] = u;
        hd[ v ] = i * 2 + 1;

        deg[ u ] ++, deg[ v ] ++;
        st.insert( minmax( u, v ) );
    }

    // 考慮每個連通塊
    for ( int i = 1 ; i <= n ; ++ i ) {
        // 有解就會結束，所以應該不能被遍歷過
        assert( not vis[ i ] );

        // 如果他沒有連其他人，那就可以考慮其他人
        if ( hd[ i ] == -1 ) {
            assert( deg[ i ] == 0 );
            continue;
        }

        // bfs整個連通塊，找到degree一樣的兩個點，放在r1跟r2裡
        int qs = 0, qe = 0;
        int r1 = -1, r2 = -1;
        qu[ qe ++ ] = i;
        vis[ i ] = true;
        while ( qs < qe ) {
            int u = qu[ qs ++ ];
            if ( sd[ deg[ u ] ] )
                r1 = u, r2 = sd[ deg[ u ] ];
            sd[ deg[ u ] ] = u;
            for ( int _ = hd[ u ] ; _ != -1 ; _ = nxt[ _ ] ) {
                if ( vis[ to[ _ ] ] ) continue;
                vis[ to[ _ ] ] = true;
                qu[ qe ++ ] = to[ _ ];
            }
        }
        // 理論上一定會找到解
        assert( r1 != -1 );
        // 重新以r1 bfs一次，找出r1->r2的一條路徑
        for ( int _ = 0 ; _ < qe ; ++ _ )
            vis[ qu[ _ ] ] = false;
        qs = 0, qe = 0;
        qu[ qe ++ ] = r1;
        vis[ r1 ] = true;
        while ( qs < qe ) {
            int u = qu[ qs ++ ];
            for ( int _ = hd[ u ] ; _ != -1 ; _ = nxt[ _ ] ) {
                if ( vis[ to[ _ ] ] ) continue;
                vis[ to[ _ ] ] = true;
                qu[ qe ++ ] = to[ _ ];
                from[ to[ _ ] ] = u;
            }
        }
        // 確實找出那條路徑
        vector< int > path;
        while( r2 != r1 ) {
            path.push_back( r2 );
            r2 = from[ r2 ];
        }
        path.push_back( r1 );

        // 確定自己走的路徑是合法的
        int xr = 0, la = -1;
        for ( size_t _ = 1 ; _ + 1 < path.size() ; ++ _ ) {
            cout << path[ _ ] << ' ';
            xr ^= deg[ path[ _ ] ];
            if ( la != -1 )
                assert( st.find( minmax( la, path[ _ ] ) ) != st.end() );
            la = path[ _ ];
        }
        for ( size_t _ = 1 ; _ <= path.size() ; ++ _ ) {
            cout << path[ path.size() - _ ] << " \n"[ _ == path.size() ];
            xr ^= deg[ path[ path.size() - _ ] ];
            if ( la != -1 )
                assert( st.find( minmax( la, path[ path.size() - _ ] ) ) != st.end() );
            la = path[ path.size() - _ ];
        }
        assert( xr == 0 );
        return 0;
    }
    // 無解應該要只有m==0的時候才會發生
    assert( false );
    return 0;
}