#include <bits/stdc++.h>
using namespace std;
int rel[50][50], tk[50], vis[50];
int x[20][3], p, alone[50];
int dfs(int i, int r, int n) {
  vis[i] = r;
  int j, k = 1;
  for (j = 1; j <= n; j++) {
    if (rel[i][j] && vis[j] == 0) {
      k += dfs(j, r, n);
    }
  }
  return k;
}
int main() {
  int n, m, i, j, k, l, l1;
  scanf("%d", &n);
  scanf("%d", &m);
  for (i = 1; i <= m; i++) {
    scanf("%d", &j);
    scanf("%d", &k);
    rel[j][k] = 1;
    rel[k][j] = 1;
  }
  l = 0;
  for (i = 1; i <= n; i++) {
    if (vis[i]) continue;
    k = dfs(i, i, n);
    if (k > 3) {
      printf("-1");
      return 0;
    }
    if (k == 1) {
      l++;
      alone[l] = i;
    }
  }
  memset(vis, 0, sizeof(vis));
  l1 = 1;
  for (i = 1; i <= n; i++) {
    if (vis[i]) continue;
    k = dfs(i, i, n);
    if (k > 1) {
      p++;
      m = 0;
      for (j = 1; j <= n; j++) {
        if (vis[j] == i) {
          x[p][m] = j;
          m++;
        }
      }
      if (k == 2) {
        if (l1 > l) {
          printf("-1");
          return 0;
        }
        x[p][2] = alone[l1];
        l1++;
      }
    }
  }
  p++;
  m = 0;
  for (i = l1; i <= l; i++) {
    x[p][m] = alone[i];
    m++;
    if (m == 3) {
      m = 0;
      p++;
    }
  }
  for (i = 1; i < p; i++) {
    for (j = 0; j < 3; j++) {
      printf("%d ", x[i][j]);
    }
    printf("\n");
  }
  return 0;
}
