///////////////////////////////////////////////////////////////////////////////

#include <bits/stdc++.h>
#include <unistd.h>
#include <time.h>
#include <sys/time.h>

using namespace std;

///////////////////////////////////////////////////////////////////////////////

#define DEBUG 0

#define pb push_back
#define V vector
#define M unordered_map
#define S static

#define rep(i,n) for(ll i=0LL; i<n; ++i)
#define srep(i,s,n) for(ll i=s; i<n; ++i)
#define rrep(i,n) for(ll i=n-1LL; i>=0LL; --i)
#define ALL(a) (a).begin(),(a).end()
#define RALL(a) (a).rbegin(),(a).rend()
#define CIN(x) do { \
        assert(!cin.eof()); \
        cin >> x; \
        assert(!cin.fail()); \
} while(0);
#if DEBUG
#define debug_print(...) _debug_print(__VA_ARGS__)
#define debug_printf(...) printf(__VA_ARGS__)
#define debug_print_time _debug_print_time
#else // DEBUG
#define debug_print(...)
#define debug_printf(...)
#define debug_print_time
#endif // DEBUG

typedef long long ll;
typedef unsigned long long ull;
typedef tuple<ll, ll> t2;
typedef tuple<ll, ll, ll> t3;
typedef tuple<ll, ll, ll, ll> t4;
typedef tuple<ll, ll, ll, ll, ll> t5;
template <typename T>
using priority_queue_incr = priority_queue<T, V<T>, greater<T> >;

///////////////////////////////////////////////////////////////////////////////

template <typename TT, typename T>
T get_m(M<TT, T> &m, TT k, T default_value)
{
    if (m.find(k) == m.end()) return m[k] = default_value;
    return m[k];
}

template <typename TT, typename T>
void incr_m(M<TT, T> &m, TT k)
{
    if (m.find(k) == m.end()) m[k] = 0;
    m[k]++;
}

template <typename TT, typename T>
void incr_m(map<TT, T> &m, TT k)
{
    if (m.find(k) == m.end()) m[k] = 0;
    m[k]++;
}

void llin(ll &a)
{
    CIN(a);
}

void llinl1(V<ll> &v, ll count)
{
    for (ll i = 0LL; i < count; ++i) {
        ll a;
        CIN(a);
        v.push_back(a);
    }
}

void llinl2(V<t2> &v, ll count)
{
    for (ll i = 0LL; i < count; ++i) {
        ll a, b;
        CIN(a >> b);
        v.push_back(t2(a, b));
    }
}

void llinl3(V<t3> &v, ll count)
{
    for (ll i = 0LL; i < count; ++i) {
        ll a, b, c;
        CIN(a >> b >> c);
        v.push_back(t3(a, b, c));
    }
}

void llinl4(V<t4> &v, ll count)
{
    for (ll i = 0LL; i < count; ++i) {
        ll a, b, c, d;
        CIN(a >> b >> c >> d);
        v.push_back(t4(a, b, c, d));
    }
}

void llina(V<ll> &v, ll count)
{
    llinl1(v, count);
}

template <typename T>
void sort(V<T> &v)
{
    sort(v.begin(), v.end());
}

template <typename T>
void sort_reverse(V<T> &v)
{
    sort(v.begin(), v.end(), greater<T>());
}

template <typename T>
void _debug_print(T x)
{
    cout << x << endl;
}

void _debug_print(const t2 &x)
{
    ll x1 = get<0>(x);
    ll x2 = get<1>(x);
    cout << "-- " << x1 << " -- " << x2 << endl;
}

void _debug_print(const t3 &x)
{
    ll x1 = get<0>(x);
    ll x2 = get<1>(x);
    ll x3 = get<2>(x);
    cout << "-- " << x1 << " -- " << x2 << " -- " << x3 << endl;
}

void _debug_print(const t4 &x)
{
    ll x1 = get<0>(x);
    ll x2 = get<1>(x);
    ll x3 = get<2>(x);
    ll x4 = get<3>(x);
    cout << "-- " << x1 << " -- " << x2
         << " -- " << x3 << " -- " << x4 << endl;
}

template <typename T>
void _debug_print(T xarray[], ll n)
{
    rep (i, n) _debug_print(xarray[i]);
}

template <typename T>
void _debug_print(const V<T> &xlist)
{
    for (auto x : xlist) {
        cout << "-- ";
        _debug_print(x);
    }
}

template <typename T>
void _debug_print(const set<T> &xset)
{
    for (auto x : xset) {
        cout << "-- ";
        _debug_print(x);
    }
}

template <typename TT, typename T>
void _debug_print(const M<TT, T> &xlist)
{
    for (auto x : xlist) {
        TT k = x.first;
        T v = x.second;
        cout << "====" << endl;
        cout << "K=";
        _debug_print(k);
        cout << "V=";
        _debug_print(v);
    }
}

template <typename TT, typename T>
void _debug_print(const map<TT, T> &xlist)
{
    for (auto x : xlist) {
        TT k = x.first;
        T v = x.second;
        cout << "====" << endl;
        cout << "K=";
        _debug_print(k);
        cout << "V=";
        _debug_print(v);
    }
}

void _debug_print_time(const char *prefix)
{
    struct timeval tv;
    gettimeofday(&tv, NULL);
#if DEBUG
    struct tm *tm = localtime(&tv.tv_sec);
#endif
    debug_printf("-- %s %02d:%02d:%02d.%06ld\n",
                 prefix, tm->tm_hour, tm->tm_min, tm->tm_sec, tv.tv_usec);
}

///////////////////////////////////////////////////////////////////////////////

void _main();
int main()
{
    cout << setprecision(12);
#if !DEBUG
    ios::sync_with_stdio(false);
    cin.tie(0);
#endif

    _main();
    return 0;
}

void make_edgelist(const V<t2> &srclist, V<ll> edgelist[])
{
    for (auto src : srclist) {
        ll a = get<0>(src);
        ll b = get<1>(src);
        edgelist[a].pb(b);
        edgelist[b].pb(a);
    }
}

void make_parental_relation(const V<ll> edgelist[], ll root, ll n,
                            ll parents[], V<ll> children[], ll levels[])
{
    queue<ll> q;
    bool checked[n+1];

    memset(checked, 0, sizeof(checked));

    q.push(root);
    checked[root] = true;
    parents[root] = root;
    levels[root] = 0LL;

    for ( ; !(q.empty()); ) {
        ll now = q.front(); q.pop();
        for (auto next : edgelist[now]) {
            if (checked[next]) continue;
            q.push(next);
            checked[next] = true;
            parents[next] = now;
            children[now].pb(next);
            levels[next] = levels[now] + 1LL;
        }
    }
}

void _main()
{
    ll n; llin(n);
    ll m; llin(m);
    S V<t2> uvlist; llinl2(uvlist,m);

    if (m & 1LL) {
        cout << -1 << endl;
        return;
    }

    S V<ll> edgelist[200005];
    make_edgelist(uvlist, edgelist);

    queue<ll> q;
    S bool checked[100005] = {};
    V<t2> tree_uvlist;
    q.push(1);
    checked[1] = true;

    while (q.size()) {
        ll v = q.front(); q.pop();
        for (auto nv : edgelist[v]) {
            if (checked[nv]) continue;
            q.push(nv);
            checked[nv] = true;
            tree_uvlist.pb(t2(v, nv));
        }
    }

    debug_printf("---- tree_uvlist\n");
    debug_print(tree_uvlist);

    S V<ll> tree_edgelist[200005];
    make_edgelist(tree_uvlist, tree_edgelist);

    S ll parents[200005];
    S V<ll> children[200005];
    S ll levels[200005];
    make_parental_relation(tree_edgelist, 1, n, parents, children, levels);

    S ll maps[200005];
    srep (v, 1, n+1) maps[v] = v;
    ll vv = n+1;

    for (auto uv : uvlist) {
        ll v1 = get<0>(uv);
        ll v2 = get<1>(uv);
        if (parents[v1] == v2) continue;
        if (parents[v2] == v1) continue;
        maps[vv] = v2;
        parents[vv] = v1;
        children[v1].pb(vv);
        levels[vv] = levels[v1] + 1LL;
        vv++;
    }

    debug_printf("---- maps\n");
    debug_print(maps, vv);
    debug_printf("---- parents\n");
    debug_print(parents, vv);
    srep (v, 1, vv) {
        debug_printf("---- children v=%lld\n", v);
        debug_print(children[v]);
    }

    S ll ccnts[200005] = {};
    srep (v, 1, vv) ccnts[v] = children[v].size();
    queue<ll> q2;
    S ll stock[200005] = {};

    srep (v, 1, vv) if (!ccnts[v]) q2.push(v);

    while (q2.size()) {
        ll v = q2.front(); q2.pop();
        ll pv = parents[v];
        if (v == pv) continue;
        if (stock[v]) {
            ll v0 = maps[pv];
            ll v1 = maps[v];
            ll v2 = maps[stock[v]];
            cout << v1 << " " << v0 << endl;
            cout << v1 << " " << v2 << endl;
            stock[v] = 0;
        }
        else if (stock[pv]) {
            ll cv0 = maps[v];
            ll cv1 = maps[stock[pv]];
            ll bv = maps[pv];
            cout << bv << " " << cv0 << endl;
            cout << bv << " " << cv1 << endl;
            stock[pv] = 0;
        }
        else {
            stock[pv] = v;
        }

        ccnts[pv]--;
        if (ccnts[pv] == 0) q2.push(pv);
    }
}

///////////////////////////////////////////////////////////////////////////////


Measured memory_bytes: 34260