#include <bits/stdc++.h>
#define int int64_t
#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
using namespace std;
using ar = array<int, 2>;
const int64_t INF = 1ll << 60;
const int N = 1e5 + 5;
vector<ar> delta[N];
int n, q, re[N], mx[N], L[N], R[N];
vector<int> M[N];
void imp() {
FOR(i, 0, n) cout << "-1 ";
exit(0);
}
signed main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
cin >> n >> q;
fill(L, L + n, -1);
fill(R, R + n, n);
while (q--) {
int l, r, x;
cin >> l >> r >> x;
L[x] = max(L[x], l);
R[x] = min(R[x], r);
delta[l].push_back({x, +1});
delta[r + 1].push_back({x, -1});
}
multiset<int> S;
vector<int> cur;
FOR(i, 0, n) {
for (auto [x, d]: delta[i]) {
if (d == 1) S.insert(x);
else S.erase(S.find(x));
}
if (S.size()) mx[i] = *S.rbegin(), M[mx[i]].push_back(i);
else cur.push_back(i);
}
FOR(i, 0, n) {
int l = L[i], r = R[i];
if (l == -1) {
if (cur.empty()) imp();
re[cur.back()] = i;
cur.pop_back();
continue;
}
if (l > r || M[i].empty()) imp();
int x = -1;
while (M[i].size()) {
x = M[i].back(); M[i].pop_back();
if (l <= x && x <= r) break;
cur.push_back(x);
}
if (!(l <= x && x <= r)) imp();
re[x] = i;
for (auto t: M[i]) cur.push_back(t);
}
FOR(i, 0, n)
cout << re[i] << ' ';
return 0;
}
