#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const int inf = 1e9;
struct Seg {
int n;
vector<int> mn;
vector<int> mx;
Seg(int n) : n(n), mn(4 * n, inf), mx(4 * n, -1) {}
void updMax(int node, int start, int end, int l, int r, int v) {
if(start > end || start > r || end < l) return;
if(start >= l && end <= r) {
mx[node] = max(mx[node], v);
return;
}
int mid = (start + end) / 2;
updMax(node << 1, start, mid, l, r, v);
updMax(node << 1 | 1, mid + 1, end, l, r, v);
}
void buildMin(int node, int start, int end, const vector<int>& b) {
if(start == end) {
mn[node] = b[start];
return;
}
int mid = (start + end) / 2;
buildMin(node << 1, start, mid, b);
buildMin(node << 1 | 1, mid + 1, end, b);
mn[node] = min(mn[node << 1], mn[node << 1 | 1]);
}
void kill(int node, int start, int end, int id) {
if(start == end) {
mn[node] = inf;
return;
}
int mid = (start + end) / 2;
if(id <= mid) kill(node << 1, start, mid, id);
else kill(node << 1 | 1, mid + 1, end, id);
mn[node] = min(mn[node << 1], mn[node << 1 | 1]);
}
void push_max(int node, int start, int end, int currMax, vector<int>& b) {
currMax = max(currMax, mx[node]);
if(start == end) {
b[start] = currMax;
return;
}
int mid = (start + end) / 2;
push_max(node << 1, start, mid, currMax, b);
push_max(node << 1 | 1, mid + 1, end, currMax, b);
}
int find(int node, int start, int end, int l, int r, int v) {
if(start > end || start > r || end < l || mn[node] > v) return -1;
if(start == end) return start;
int mid = (start + end) / 2;
int res = find(node << 1, start, mid, l, r, v);
if(res == -1) res = find(node << 1 | 1, mid + 1, end, l, r, v);
return res;
}
};
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
int n, q;
cin >> n >> q;
vector<int> L(n), R(n, n - 1);
vector<char> have(n, 0);
Seg seg(n);
for (int i = 0; i < q; ++i) {
int l, r, v;
cin >> l >> r >> v;
seg.updMax(1, 0, n - 1, l, r, v);
L[v] = max(L[v], l);
R[v] = min(R[v], r);
have[v] = 1;
}
auto die = [&]() {
for (int j = 0; j < n; ++j) {
cout << -1 << " ";
}
exit(0);
};
for (int i = 0; i < n; ++i)
if(have[i] && L[i] > R[i])
die();
vector<int> B(n);
seg.push_max(1, 0, n - 1, 0, B);
seg.buildMin(1, 0, n - 1, B);
vector<tuple<int, int, int>> vals(n);
for (int i = 0; i < n; ++i) vals[i] = {i, L[i], R[i]};
sort(vals.begin(), vals.end(), [](const tuple<int, int, int>& a, const tuple<int, int, int>& b) { return get<2>(a) < get<2>(b);});
vector<int> res(n, -1);
for (int i = 0; i < n; ++i) {
auto &[v, l, r] = vals[i];
int p = seg.find(1, 0, n - 1, l, r, v);
if(~p) {
res[p] = v;
seg.kill(1, 0, n - 1, p);
}
else die();
}
for (int &i : res)
cout << i << " ";
return 0;
}
