#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
template<class T> using V = vector<T>;
using VI = V<int>;
using VL = V<ll>;
using VS = V<string>;
template<class T> using PQ = priority_queue<T, V<T>, greater<T>>;
using graph = V<VI>;
template<class T> using w_graph = V<V<pair<int, T>>>;
#define FOR(i,a,n) for(int i=(a);i<(n);++i)
#define eFOR(i,a,n) for(int i=(a);i<=(n);++i)
#define rFOR(i,a,n) for(int i=(n)-1;i>=(a);--i)
#define erFOR(i,a,n) for(int i=(n);i>=(a);--i)
#define all(a) a.begin(),a.end()
#define rall(a) a.rbegin(),a.rend()
#define out(y,x) ((y)<0||h<=(y)||(x)<0||w<=(x))
#ifdef _DEBUG
#define line cout << "-----------------------------\n"
#define stop system("pause")
#endif
constexpr ll INF = 1000000000;
constexpr ll LLINF = 1LL << 61;
constexpr ll mod = 1000000007;
constexpr ll MOD = 998244353;
constexpr ld eps = 1e-10;
template<class T>inline bool chmax(T& a, const T& b) { if (a < b) { a = b; return true; }return false; }
template<class T>inline bool chmin(T& a, const T& b) { if (a > b) { a = b; return true; }return false; }
inline void init() { cin.tie(nullptr); cout.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(15); }
template<class T>inline istream& operator>>(istream& is, V<T>& v) { for (auto& a : v)is >> a; return is; }
template<class T, class U>inline istream& operator>>(istream& is, pair<T, U>& p) { is >> p.first >> p.second; return is; }
template<class T>inline V<T> vec(size_t a) { return V<T>(a); }
template<class T>inline V<T> defvec(T def, size_t a) { return V<T>(a, def); }
template<class T, class... Ts>inline auto vec(size_t a, Ts... ts) { return V<decltype(vec<T>(ts...))>(a, vec<T>(ts...)); }
template<class T, class... Ts>inline auto defvec(T def, size_t a, Ts... ts) { return V<decltype(defvec<T>(def, ts...))>(a, defvec<T>(def, ts...)); }
template<class T>inline void print(const T& a) { cout << a << "\n"; }
template<class T, class... Ts>inline void print(const T& a, const Ts&... ts) { cout << a << " "; print(ts...); }
template<class T>inline void print(const V<T>& v) { for (int i = 0; i < v.size(); ++i)cout << v[i] << (i == v.size() - 1 ? "\n" : " "); }
template<class T>inline void print(const V<V<T>>& v) { for (auto& a : v)print(a); }
template<class T>inline T sum(const V<T>& a, int l, int r) { return 0 <= l && l <= r && r < a.size() ? a[r] - (l == 0 ? 0 : a[l - 1]) : 0; }
template<class T>inline void END(T s) { print(s); exit(0); }
void END() { exit(0); }

template<class Op> class SegmentTree {
	using T = typename Op::T;
	int len, n;
	vector<T> dat;
public:
	SegmentTree(const int _n) : n(_n) {
		for (len = 1; len < n; len <<= 1);
		dat.resize(len << 1, Op::unit);
	}
	SegmentTree(const vector<T>& v) : n(v.size()) {
		for (len = 1; len < n; len <<= 1);
		dat.resize(len << 1, Op::unit);
		for (int i = 0; i < n; ++i)dat[i + len] = v[i];
		for (int i = len - 1; 0 < i; --i)
			dat[i] = Op::merge(dat[i << 1], dat[i << 1 | 1]);
	}
	inline void update(int idx, const T a) {
		idx += len;
		dat[idx] = Op::update(dat[idx], a);
		for (idx >>= 1; 0 < idx; idx >>= 1)
			dat[idx] = Op::merge(dat[idx << 1], dat[idx << 1 | 1]);
	}
	inline T value(int l, int r) {
		T vl = Op::unit, vr = Op::unit;
		for (l += len, r += len; l < r; l >>= 1, r >>= 1) {
			if (l & 1)vl = Op::merge(vl, dat[l++]);
			if (r & 1)vr = Op::merge(dat[--r], vr);
		}
		return Op::merge(vl, vr);
	}
	inline T operator[](int idx) { return dat[idx + len]; }
};
template<class Type> struct node {
	using T = Type;
	inline static T unit = mod;
	inline static T merge(T vl, T vr) { return min(vl, vr); }
	inline static T update(T vl, T vr) { return vr; }
};
int main() {
    init();

    int n, q; cin >> n >> q;
    V<tuple<int, int, int>> blr(q);
    for (auto& [b, l, r] : blr) {
        cin >> l >> r >> b;
        --l;
    }
    sort(rall(blr));

    set<int> se;
    eFOR(i, 0, n)se.insert(i);
    VI a(n, mod);
	SegmentTree<node<int>> seg(n);
    for (auto [b, l, r] : blr) {
		int cnt = seg.value(l, r) == b;
        for (int i = l; i < r; se.erase(i), i = *se.upper_bound(i)) {
            if (a[i] != mod)continue;
            a[i] = b;
			seg.update(i, b);
            ++cnt;
        }
        if (cnt == 0)END(-1);
    }
    print(a);

    return 0;
}