#include <bits/stdc++.h>
using namespace std;
const int N = 1e5+10;
int n, Q, Li[N], Lu[N], Ri[N], Ru[N], ans[N];
set<int> rem_pos, rem_val;
void ex(){
for(int i = 0; i < n; i++) cout << "-1 ";
exit(0);
}
int main(void){
ios_base::sync_with_stdio(0); cin.tie(0);
cin >> n >> Q;
for(int i = 0; i < n; i++){
Li[i] = Ru[i] = -1e9;
Lu[i] = Ri[i] = 1e9;
rem_pos.insert(i);
rem_val.insert(i);
}
for(int i = 0; i < Q; i++){
int l, r, x; cin >> l >> r >> x;
Li[x] = max(Li[x], l), Ri[x] = min(Ri[x], r);
Lu[x] = min(Lu[x], l), Ru[x] = max(Ru[x], r);
}
for(int i = n-1; i >= 0; i--){
if(Li[i] == -1e9) continue;
if(Li[i] > Ri[i]) ex();
auto itp = rem_pos.lower_bound(Li[i]);
if(itp == rem_pos.end() or *itp > Ri[i]) ex();
ans[*itp] = i;
rem_pos.erase(itp), rem_val.erase(i);
while(!rem_pos.empty()){
itp = rem_pos.lower_bound(Lu[i]);
if(itp == rem_pos.end() or *itp > Ru[i]) break;
int v = *(rem_val.rbegin());
if(v < i) ex();
ans[*itp] = v;
rem_pos.erase(itp), rem_val.erase(v);
}
}
while(!rem_pos.empty()){
ans[*(rem_pos.begin())] = *rem_val.begin();
rem_pos.erase(rem_pos.begin()), rem_val.erase(rem_val.begin());
}
for(int i = 0; i < n; i++) cout << ans[i] << " ";
cout << "\n";
return 0;
}
