B

#define _CRT_SECURE_NO_DEPRECATE
#define _SECURE_SCL 0
#pragma comment(linker, "/STACK:300000000")

#include <algorithm>
#include <bitset>
#include <cassert>
#include <cctype>
#include <complex>
#include <ctime>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <deque>
#include <functional>
#include <fstream>
#include <iostream>
#include <iomanip>
#include <map>
#include <memory.h>
#include <numeric>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <sstream>
#include <vector>
#include <utility>
#include <cmath>
using namespace std;

#define pb push_back
#define mp make_pair
#define sz(a) (int)(a).size()
#define all(a) (a).begin(), (a).end()
#define rall(a) (a).rbegin(), (a).rend()

#define forn(i,n) for (int i=0; i<int(n); ++i)
#define fornd(i,n) for (int i=int(n)-1; i>=0; --i)
#define forab(i,a,b) for (int i=int(a); i<int(b); ++i)

typedef long long ll;
typedef long double ld;
typedef unsigned long long ull;

const int INF = (int) 1e9;
const long long INF64 = (long long) 1e18;
const long double eps = 1e-9;
const long double pi = 3.14159265358979323846;

int g[50][50], n, m;
bool used[50];

vector <int> cur;

vector <vector <int> > c[50];

void dfs(int v){
    used[v] = true;
    cur.pb(v);
    for (int i=1; i<=n; i++)
        if (g[v][i] && !used[i])
            dfs(i);
}

int main(){
#ifdef dudkamaster
    freopen("input.txt","rt",stdin);
    freopen("output.txt","wt",stdout);
#endif
    memset(g, 0, sizeof(g));
    memset(used, 0, sizeof(used));
    cin >> n >> m;
    for (int i=0; i<m; i++){
        int a,b;
        cin >> a >> b;
        g[a][b] = g[b][a] = 1;
    }
    for (int i=1; i<=n; i++){
        if (!used[i]){
            cur.clear();
            dfs(i);
            c[sz(cur)].pb(cur);
        }
    }
    vector <vector <int> > out = c[3];
    for (int i=4; i<50; i++){
        if (sz(c[i])!=0){
            cout << -1;
            return 0;
        }
    }
    if (sz(c[2])>sz(c[1])){
        cout << -1;
        return 0;
    }
    if ((sz(c[1])-sz(c[2])) % 3 != 0){
        cout << -1;
        return 0;
    }
    forn(i,sz(c[2])){
        vector <int> tout;
        tout.pb(c[2][i][0]);
        tout.pb(c[2][i][1]);
        tout.pb(c[1][i][0]);
        out.pb(tout);
    }
    for (int i=sz(c[2]); i<sz(c[1]); i += 3){
        vector <int> tout;
        forn(j,3)
            tout.pb(c[1][i+j][0]);
        out.pb(tout);
    }
    forn(i,n/3){
        forn(j,3)
            cout << out[i][j] << ' ';
        cout << endl;
    }

    return 0;
}