#include <bits/stdc++.h>
using namespace std;
 
#define rep(i,j,n) for(int i=j;i<n;++i)
#define all(i) i.begin(),i.end()
#define rall(i) i.rbegin(), i.rend()
#define INF 1e9
#define LINF 1e18
// const int mod = 998244353;
const int mod = 1000000007;
 
using i64 = long long;
using pi = pair<int, int>;
 
template <class T> using vt = vector<T>;
template <class T> using vvt = vector<vector<T>>;
 
i64 gcd(i64 n, i64 m) {return (m == 0? n : gcd(m, n % m));}
i64 lcm(i64 n, i64 m) {return (n / gcd(n, m) * m);}
int dx[] = {1, 0, -1, 0};
int dy[] = {0, 1, 0, -1};

#include <vector>
#include <functional>

template <class Monoid, class OperatorMonoid = Monoid> class LazySegmentTree {
  using F = std::function<Monoid(Monoid, Monoid)>;
  using G = std::function<Monoid(Monoid, OperatorMonoid, int)>;
  using H = std::function<OperatorMonoid(OperatorMonoid, OperatorMonoid)>;

  private:
    int n;
    std::vector<Monoid> seg;
    std::vector<OperatorMonoid> lazy;

    const F f;
    const G g;
    const H h;
    const Monoid M1;
    const OperatorMonoid OM1;

    void lazyUpdate(int k, int l, int r) {
      if(lazy[k] == OM1) return;

      if(2 * k + 1 < 2 * n - 1) {
        lazy[2 * k + 1] = h(lazy[2 * k + 1], lazy[k]);
        lazy[2 * k + 2] = h(lazy[2 * k + 2], lazy[k]);
      }
      seg[k] = g(seg[k], lazy[k], r - l);
      lazy[k] = OM1;
    }

  public:
    LazySegmentTree(int sz, const F f, const G g, const H h, const Monoid &M1, const OperatorMonoid &OM1) : f(f), g(g), h(h), M1(M1), OM1(OM1) {
      n = 1;
      while(n < sz) n *= 2;
      seg.resize(2 * n - 1, M1);
      lazy.resize(2 * n - 1, OM1);
    }

    void update(int a, int b, Monoid x, int k = 0, int l = 0, int r = -1) {
      if(r < 0) r = n;

      lazyUpdate(k, l, r);

      if(b <= l || r <= a) return;

      if(a <= l && r <= b) {
        lazy[k] = h(lazy[k], x);
        lazyUpdate(k, l, r);
      }
      else {
        update(a, b, x, 2 * k + 1, l, (l + r) / 2);
        update(a, b, x, 2 * k + 2, (l + r) / 2, r);
        seg[k] = f(seg[k * 2 + 1], seg[k * 2 + 2]);
      }
    }

    Monoid query(int a, int b, int k = 0, int l = 0, int r = -1) {
      if(r < 0) r = n;

      lazyUpdate(k, l, r);

      if(b <= l || r <= a) return M1;
      if(a <= l && r <= b) return seg[k];
      Monoid vl = query(a, b, 2 * k + 1, l, (l + r) / 2);
      Monoid vr = query(a, b, 2 * k + 2, (l + r) / 2, r);
      return f(vl, vr);
    }
};

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);

  int n, q;
  cin >> n >> q;
  vt<int> l(q), r(q), b(q);
  rep(i, 0, q) cin >> l[i] >> r[i] >> b[i];
  rep(i, 0, q) l[i]--;

  vt<int> idx(q);
  iota(all(idx), 0);
  sort(all(idx), [&](const int &i, const int &j){ return b[i] < b[j]; });

  LazySegmentTree<int> seg(n, [](int a, int b){ return min(a, b); },
                            [](int a, int b, int len){ if(a == INF) return b; else return max(a, b); },
                            [](int a, int b){ return max(a, b); }, INF, 0);

  rep(i, 0, q) {
    seg.update(l[idx[i]], r[idx[i]], b[idx[i]]);
  }

  rep(i, 0, q) {
    if(seg.query(l[i], r[i]) != b[i]) return cout << -1 << endl, 0;
  }
  rep(i, 0, n) {
    cout << seg.query(i, i + 1) << " \n"[i == n - 1];
  }
}