#include <bits/stdc++.h>
using namespace std;
#include <atcoder/all>
using namespace atcoder;
#define rep(i,a,b) for(int i=a;i<b;i++)

int op(int a,int b){return min(a,b);}
int e(){return 1e9;}

int main(){
  int n,q;cin>>n>>q;
  vector<vector<pair<int,int>>> g(n);
  rep(i,0,q){
    int l,r,b;cin>>l>>r>>b;
    g[l-1].emplace_back(b,r);
  }
  priority_queue<pair<int,int>> que;
  vector<int> a(n);
  que.push({1,n});
  rep(i,0,n){
    for(auto j:g[i])que.push(j);
    while(que.top().second<=i)que.pop();
    a[i]=que.top().first;
  }
  segtree<int,op,e> seg(a);
  rep(i,0,n)for(auto [v,j]:g[i])
    if(seg.prod(i,j)!=v){
      cout<<-1<<endl;
      return 0;
    }
  for(int i:a)cout<<i<<' ';
  cout<<endl;
}