#include <bits/stdc++.h>
using namespace std;
const int INF = 1000000000;
template <typename T>
struct sparse_table{
	vector<vector<T>> ST;
	sparse_table(vector<T> &A){
		int N = A.size();
		int LOG = 32 - __builtin_clz(N);
		ST = vector<vector<T>>(LOG, vector<T>(N));
		for (int i = 0; i < N; i++){
			ST[0][i] = A[i];
		}
		for (int i = 0; i < LOG - 1; i++){
			for (int j = 0; j < N - (1 << i); j++){
				ST[i + 1][j] = min(ST[i][j], ST[i][j + (1 << i)]);
			}
		}
	}
	T range_min(int L, int R){
		int d = 31 - __builtin_clz(R - L);
		return min(ST[d][L], ST[d][R - (1 << d)]);
	}
};
int main(){
  int N, Q;
  cin >> N >> Q;
  vector<int> l(Q), r(Q), B(Q);
  for (int i = 0; i < Q; i++){
    cin >> l[i] >> r[i] >> B[i];
    l[i]--;
  }
  vector<vector<int>> add(N + 1), sub(N + 1);
  for (int i = 0; i < Q; i++){
    add[l[i]].push_back(B[i]);
    sub[r[i]].push_back(B[i]);
  }
  multiset<int> st;
  st.insert(1);
  vector<int> A(N);
  for (int i = 0; i < N; i++){
    for (int x : add[i]){
      st.insert(x);
    }
    for (int x : sub[i]){
      st.erase(st.find(x));
    }
    A[i] = *prev(st.end());
  }
  sparse_table<int> ST(A);
  bool ok = true;
  for (int i = 0; i < Q; i++){
    if (ST.range_min(l[i], r[i]) != B[i]){
      ok = false;
    }
  }
  if (!ok){
    cout << -1 << endl;
  } else {
    for (int i = 0; i < N; i++){
      cout << A[i];
      if (i < N - 1){
        cout << ' ';
      }
    }
    cout << endl;
  }
}