#include "bits/stdc++.h"
#include <atcoder/all>
using namespace std;
using namespace atcoder;
using ll = long long;
using vl = vector<long long>;
using pl = pair<long long, long long>;
struct edge {long long to;long long cost;edge(long long t,long long c):to(t),cost(c){}};
using Graph = vector<vector<long long>>;
using WGraph = vector<vector<edge>>;
constexpr int dx[8]{1,0,-1,0,1,1,-1,-1};
constexpr int dy[8]{0,1,0,-1,1,-1,1,-1};
#define rep(i, n) for(long long (i) = 0; (i) < (n); (i)++)
#define reps(i, a, b) for(long long (i) = (a); (i) < (b); (i)++)
#define rrep(i, a, b) for(long long (i) = (a); (i) >= (b); (i)--)
#define all(v) (v).begin(), (v).end()
#define pb push_back
#define V vector
constexpr long long MOD1 = 1000000007;
constexpr long long MOD9 =  998244353;
constexpr long long INF = 1000000000;
constexpr long long LL_MAX = std::numeric_limits<long long>::max();
long long safe_mod(long long n, long long m){if(n >= 0) {return n % m;} else return (n%m + m)%m;}
long long div_ceil(long long a, long long b){return (a + b - 1) / b;}
long long pw(long long x,long long n) {ll ret=1;while(n>0){if(n&1){ret=ret*x;}if(n>>=1){x=x*x;}}return ret;}
template<typename T> T SUM(const vector<T> &v){T ret{};return(accumulate(v.begin(), v.end(), ret));}
template<typename T> T MAX(const vector<T> &v){return *max_element(v.begin(), v.end());}
template<typename T> T MIN(const vector<T> &v){return *min_element(v.begin(), v.end());}
template<typename T> T pwmod(T x, long long n, long long m) {T ret=1;while(n>0){if(n&1)ret=ret*x%m;x=x*x%m;n>>=1;}return ret%m;}
template<typename T> void rsort(vector<T> &v) {sort(v.begin(), v.end(), greater<T>());}
template<typename T> bool chmax(T &a, const T& b) {if(a<b){a=b;return true;}return false;}
template<typename T> bool chmin(T &a, const T& b) {if(a>b){a=b;return true;}return false;}
template<typename T, typename S> pair<T, S> mp(const T &a, const S &b){return make_pair(a, b);}
template<typename T> void uniquify(vector<T> &v){sort(v.begin(), v.end()); v.erase(unique(v.begin(), v.end()), v.end());}
template<typename T,typename S> ostream&operator<<(ostream&os,const pair<T,S>&p){os<<"("<<p.first<<", "<<p.second<<")";return os;}
template<typename T,typename S> ostream&operator<<(ostream&os,const map<T,S>&ma){for(auto [a,b]:ma){os<<"("<<a<<", "<<b<<")"<<" ";}return os;}
template<typename T> ostream &operator<<(ostream&os,const set<T>&s){os<<"{";for(auto c:s)os<<c<<" ";os<<"}";return os;}
template<typename T> ostream &operator<<(ostream&os,const vector<T>&v){os<<"[";for(int i=0;i<v.size();i++){os<<v[i]<<(i==v.size()-1?"":" ");}os<<"]";return os;}
template<typename T> vector<int> compress(vector<T> &a){
    int n = a.size(); vector<int> ret(n); vector<T> temp = a;
    sort(a.begin(), a.end()); a.erase(unique(a.begin(), a.end()), a.end());
    for(int i = 0; i < n; i++) ret[i] = lower_bound(a.begin(), a.end(), temp[i]) - a.begin();
    return ret;
}

//#define ONLINE_JUDGE
#ifdef ONLINE_JUDGE
#define dump(x) true
#else
#define dump(x) cerr << __LINE__ << " : " << #x << " = " << (x) << endl
#endif

ll op(ll a, ll b){return min(a, b);}
ll e(){return INF;}

void solve(){
    ll n, q; cin >> n >> q;
    V<vl> L(n+1), R(n+1);
    V<tuple<ll, ll, ll>> Query(q);
    rep(i, q){
        ll l, r, b; cin >> l >> r >> b;
        l--;
        L[l].pb(b);
        R[r].pb(b);
        Query[i] = {l, r, b};
    }
    multiset<ll> rest;
    segtree<ll, op, e> seg(n);
    rest.insert(1);
    rep(i, n){
        for(ll t : R[i]){
            auto iter = rest.find(t);
            rest.erase(iter);
        }
        for(ll t : L[i])
            rest.insert(t);
        seg.set(i, *rest.rbegin());
    }
    rep(i, q){
        auto [l, r, b] = Query[i];
        if(seg.prod(l, r) != b){
            cout << -1 << '\n';
            return;
        }
    }
    rep(i, n){
        cout << seg.get(i);
        if(i != n - 1) cout << ' ';
    }
    cout << '\n';
}

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cout << std::fixed << std::setprecision(15);

    solve();

    return 0;
}