#include <bits/stdc++.h>
using namespace std;
using ll=long long;
using Graph=vector<vector<int>>;
#define INF 1000000000

int n=1;

vector<int> tree1;
void update(int a,int b,int x,int i,int left,int right){
  if(a<=left&&right<=b){
    tree1[i]=max(tree1[i],x);
    return;
  }
  if(right<=a||b<=left){
    return;
  }
  update(a,b,x,2*i+1,left,(left+right)/2);
  update(a,b,x,2*i+2,(left+right)/2,right);
}

vector<int> tree2;
int solve(int a,int b,int i,int left,int right){
  if(a<=left&&right<=b){
    return tree2[i];
  }
  if(right<=a||b<=left){
    return INF;
  }
  int x=solve(a,b,2*i+1,left,(left+right)/2);
  int y=solve(a,b,2*i+2,(left+right)/2,right);
  return min(x,y);
}

int main(){
  int N,Q;
  cin>>N>>Q;
  while(n<N){
    n<<=1;
  }
  vector<int> l(Q),r(Q),B(Q);
  for(int i=0;i<Q;i++){
    cin>>l[i]>>r[i]>>B[i];
    l[i]--;
  }

  tree1.assign(2*n-1,1);
  tree2.assign(2*n-1,INF);

  for(int i=0;i<Q;i++){
    update(l[i],r[i],B[i],0,0,n);
  }
  for(int i=1;i<2*n-1;i++){
    tree1[i]=max(tree1[i],tree1[(i-1)/2]);
  }
  for(int i=0;i<N;i++){
    tree2[n-1+i]=tree1[n-1+i];
  }
  for(int i=n-2;i>=0;i--){
    tree2[i]=min(tree2[2*i+1],tree2[2*i+2]);
  }

  for(int i=0;i<Q;i++){
    if(B[i]!=solve(l[i],r[i],0,0,n)){
      cout<<-1<<'\n';
      return 0;
    }
  }

  for(int i=0;i<N-1;i++){
    cout<<tree1[n-1+i]<<' ';
  }
  cout<<tree1[n-1+N-1]<<'\n';
}