#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pll pair<ll, ll>
#define pii pair<int, int>
#define fs first
#define sc second
#define pb push_back
void solve() {
int n,q;
cin>>n>>q;
vector<pii> seg[n];
while(q--){
int l,r,x;
cin>>l>>r>>x;
seg[l].pb({r,x});
}
int a[n];
priority_queue<pii> pq;
for(int i=0;i<n;i++){
for(auto[r,x]:seg[i]){
pq.push({x,r});
}
while(!pq.empty()&&pq.top().sc<i)pq.pop();
if(pq.empty())a[i]=0;
else a[i]=pq.top().fs;
}
int sp[n][20];
for(int i=0;i<n;i++)sp[i][0]=a[i];
for(int x=1;x<20;x++){
for(int i=0;i+(1<<x)<=n;i++)sp[i][x]=min(sp[i][x-1],sp[i+(1<<x-1)][x-1]);
}
for(int i=0;i<n;i++){
for(auto[r,x]:seg[i]){
int k=31-__builtin_clz(r-i+1);
if(min(sp[i][k],sp[r-(1<<k)+1][k])!=x){
for(int i=0;i<n;i++)cout<<"-1 ";
cout<<'\n';
return;
}
}
}
for(int i=0;i<n;i++)cout<<a[i]<<' ';
cout<<'\n';
}
int main() {
#ifdef FPO
freopen("in","r",stdin);
freopen("out","w",stdout);
#endif
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
solve();
}
