#include<bits/stdc++.h>
using namespace std;
#define int long long
#define inf 5e18
#define nl '\n'
int lg2(int x){
int p = 0;
while((1ll<<(p+1)) <= x) p++;
return p;
}
inline void solve(){
int n, q;
cin>>n>>q;
vector<int> l[n], r[n];
vector<tuple<int,int,int>> qry;
while(q--){
int li, ri, x;
cin>>li>>ri>>x;
qry.push_back({li, ri, x});
l[li].push_back(x);
r[ri].push_back(x);
}
multiset<int> st;
int ans[n];
for(int i=0; i<n; i++){
for(int x : l[i]) st.insert(x);
ans[i] = (st.empty() ? 0 : *st.rbegin());
for(int x : r[i]) st.erase(st.find(x));
}
int m[n][17];
for(int i=0; i<n; i++) m[i][0] = ans[i];
for(int j=1; j<17; j++){
for(int i=0; i+(1<<j)-1<n; i++){
m[i][j] = min(m[i][j-1], m[i+(1<<(j-1))][j-1]);
}
}
for(auto [li, ri, x] : qry){
int lg = lg2(ri-li+1);
if(x != min(m[li][lg], m[ri-(1<<lg)+1][lg])){
for(int i=0; i<n; i++) ans[i] = -1;
break;
}
}
for(int i=0; i<n; i++) cout<<ans[i]<<" ";
}
signed main(){
ios_base::sync_with_stdio(0);
cin.tie(NULL);cout.tie(NULL);
int t = 1;
//cin>>t;
while(t--) solve();
return 0;
}
