#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
typedef long long int ll;
typedef long double ld;
#define FOR(i,l,r) for(ll i=l;i<r;i++)
#define REP(i,n) FOR(i,0,n)
#define RFOR(i,l,r) for(ll i=r-1;i>=l;i--)
#define RREP(i,n) RFOR(i,0,n)
#define ALL(x) x.begin(),x.end()
#define P pair<ll,ll>
#define F first
#define S second
#define BS(A,x) binary_search(ALL(A),x)
#define LB(A,x) (ll)(lower_bound(ALL(A),x)-A.begin())
#define UB(A,x) (ll)(upper_bound(ALL(A),x)-A.begin())
#define COU(A,x) UB(A,x)-LB(A,x)
template<typename T>using min_priority_queue=priority_queue<T,vector<T>,greater<T>>;
using mint=modint1000000007;
ll op(ll a,ll b){return min(a,b);}
ll e(){return 1e18;}
ll mapping(ll f,ll x){return max(f,x);}
ll composition(ll f,ll g){return max(f,g);}
ll id(){return -1;}
signed main(){
  ll N,Q;cin>>N>>Q;vector<ll>l(Q),r(Q),B(Q),A(N,1);REP(i,Q)cin>>l[i]>>r[i]>>B[i];
  lazy_segtree<ll,op,e,ll,mapping,composition,id>seg(A);
  REP(i,Q)seg.apply(l[i]-1,r[i],B[i]);REP(i,N)A[i]=seg.get(i);
  REP(i,Q)if(seg.prod(l[i]-1,r[i])!=B[i]){cout<<-1<<endl;return 0;}
  REP(i,N-1)cout<<A[i]<<" ";cout<<A[N-1]<<endl;
  return 0;
}