#pragma region Macros
#include <bits/stdc++.h>
#define rep(i, n) for(int(i) = 0; (i) < (n); (i)++)
#define rrep(i, n) for(int(i) = (n)-1; (i) >= 0; (i)--)
#define FOR(i, m, n) for(int(i) = (m); (i) < (n); (i)++)
#define ROF(i, m, n) for(int(i) = (n)-1; (i) >= (m); (i)--)
#define ALL(v) (v).begin(), (v).end()
#define LLA(v) (v).rbegin(), (v).rend()
#define SZ(v) (int)(v).size()
#define INT(...)     \
    int __VA_ARGS__; \
    read(__VA_ARGS__)
#define LL(...)     \
    ll __VA_ARGS__; \
    read(__VA_ARGS__)
#define DOUBLE(...)     \
    double __VA_ARGS__; \
    read(__VA_ARGS__)
#define CHAR(...)     \
    char __VA_ARGS__; \
    read(__VA_ARGS__)
#define STRING(...)     \
    string __VA_ARGS__; \
    read(__VA_ARGS__)
#define VEC(type, name, size) \
    vector<type> name(size);  \
    read(name)
#define VEC2(type, name, height, width)                     \
    vector<vector<type>> name(height, vector<type>(width)); \
    read(name)
#define DVEC(type, name1, name2, size)     \
    vector<type> name1(size), name2(size); \
    read(name1, name2)
#define TVEC(type, name1, name2, name3, size)           \
    vector<type> name1(size), name2(size), name3(size); \
    read(name1, name2, name3)
using namespace std;
using ll = long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
const int INF = 1 << 30;
const ll LINF = 1LL << 60;
const int MOD = 1e9 + 7;
const char newl = '\n';
const int dx[] = {1, 0, -1, 0};
const int dy[] = {0, 1, 0, -1};
template <class T> inline bool between(T x, T l, T r) {
    return l <= x && x < r;
}
template <class T> inline vector<T> make_vec(size_t a, T val) {
    return vector<T>(a, val);
}
template <class... Ts> inline auto make_vec(size_t a, Ts... ts) {
    return vector<decltype(make_vec(ts...))>(a, make_vec(ts...));
}
void read() {}
template <class T> inline void read(T &a) { cin >> a; }
template <class T, class S> inline void read(pair<T, S> &p) {
    read(p.first), read(p.second);
}
template <class T> inline void read(vector<T> &v) {
    for(auto &&a : v)
        read(a);
}
template <class T, class U> inline void read(vector<T> &a, vector<U> &b) {
    for(int i = 0; i < a.size(); i++) {
        read(a[i]);
        read(b[i]);
    }
}
template <class T, class U, class V>
inline void read(vector<T> &a, vector<U> &b, vector<V> &c) {
    for(int i = 0; i < a.size(); i++) {
        read(a[i]);
        read(b[i]);
        read(c[i]);
    }
}
template <class Head, class... Tail>
inline void read(Head &head, Tail &...tail) {
    read(head), read(tail...);
}
template <class T> void _write(const T &a) { cout << a; }
template <class T, class U> void _write(const std::pair<T, U> &a) { cout << a.first << ' ' << a.second; }
template <class T> void write(const T &a) {
    _write(a);
    cout << newl;
}
template <class T> void write(const vector<T> &a) {
    for(int i = 0; i < a.size(); i++) {
        _write(a[i]);
        cout << (i + 1 == a.size() ? newl : ' ');
    }
}
template <class Head, class... Tail>
void write(const Head &head, const Tail &...tail) {
    _write(head);
    cout << ' ';
    write(tail...);
}
template <class T> void writel(const T &a) { cout << a << '\n'; }
template <class T> void writel(const vector<T> &a) {
    for(int i = 0; i < a.size(); i++) {
        _write(a[i]);
        cout << newl;
    }
}
template <class Head, class... Tail>
void writel(const Head &head, const Tail &...tail) {
    _write(head);
    cout << newl;
    write(tail...);
}
template <class T> void _debug(const T &a) { cerr << a; }
template <class T, class U> void _debug(const std::pair<T, U> &a) { cerr << a.first << ' ' << a.second; }
template <class T> void debug(const T &a) {
    _debug(a);
    cerr << newl;
}
template <class T> void debug(const vector<T> &a) {
    for(int i = 0; i < a.size(); i++) {
        _debug(a[i]);
        cerr << (i + 1 == a.size() ? newl : ' ');
    }
}
template <class Head, class... Tail>
void debug(const Head &head, const Tail &...tail) {
    _debug(head);
    cerr << ' ';
    debug(tail...);
}
template <class T> void debugl(const T &a) { cerr << a << '\n'; }
template <class T> void debugl(const vector<T> &a) {
    for(int i = 0; i < a.size(); i++) {
        _debug(a[i]);
        cerr << newl;
    }
}
template <class Head, class... Tail>
void debugl(const Head &head, const Tail &...tail) {
    _debug(head);
    cerr << newl;
    debug(tail...);
}
template <class T> auto sum(const vector<T> &a) {
    return accumulate(ALL(a), T(0));
}
template <class T> auto min(const vector<T> &a) { return *min_element(ALL(a)); }
template <class T> auto max(const vector<T> &a) { return *max_element(ALL(a)); }
template <class T, class U> void msort(vector<T> &a, vector<U> &b) {
    assert(a.size() == b.size());
    vector<pair<T, U>> ab(a.size());
    for(int i = 0; i < a.size(); i++)
        ab[i] = {a[i], b[i]};
    sort(ALL(ab));
    for(int i = 0; i < a.size(); i++) {
        a[i] = ab[i].first;
        b[i] = ab[i].second;
    }
}
template <class T, class U, class V>
void msort(vector<T> &a, vector<U> &b, vector<V> &c) {
    assert(a.size() == b.size() && b.size() == c.size());
    vector<tuple<T, U, V>> abc(a.size());
    for(int i = 0; i < a.size(); i++)
        abc[i] = {a[i], b[i], c[i]};
    sort(ALL(abc));
    for(int i = 0; i < a.size(); i++) {
        a[i] = get<0>(abc[i]);
        b[i] = get<1>(abc[i]);
        c[i] = get<2>(abc[i]);
    }
}
template <class T, class U> inline bool chmax(T &a, U b) {
    if(a < b) {
        a = b;
        return 1;
    }
    return 0;
}
template <class T, class U> inline bool chmin(T &a, U b) {
    if(a > b) {
        a = b;
        return 1;
    }
    return 0;
}
int digit(ll a) {
    ll ret = 0;
    while(a && ++ret)
        a /= 10;
    return ret;
}
int digit_sum(ll a) {
    ll ret = 0;
    while(a) {
        ret += a % 10;
        a /= 10;
    }
    return ret;
}
ll llpow(ll a, ll n) {
    ll ret = 1;
    rep(i, n) ret *= a;
    return ret;
}
inline int bsf(int v) { return __builtin_ctz(v); } // 最下位の1が下から何番目か
inline int bsf(ll v) { return __builtin_ctzll(v); }
inline int bsr(int v) {
    return 31 - __builtin_clz(v);
} // 最上位の1が下から何番目か
inline int bsr(ll v) { return 63 - __builtin_clzll(v); }
inline int lsb(int v) { return v & -v; } // 最下位の1だけ残す
inline ll lsb(ll v) { return v & -v; }
inline int msb(int v) { return 1 << bsr(v); } // 最上位の1だけ残す
inline ll msb(ll v) { return 1LL << bsr(v); }
struct IO {
    IO() {
        ios::sync_with_stdio(false);
        cin.tie(nullptr);
        cout << fixed << setprecision(10);
    }
} io;
#pragma endregion

template <class S, class F> class LazySegTree {
  private:
    using Op = function<S(S, S)>;
    using Mapping = function<S(S, F)>;
    using Composition = function<F(F, F)>;

    int n;
    int org_size;
    const Op op;
    const Mapping mapping;
    const Composition composition;
    const S e;
    const F oe;
    vector<S> node;
    vector<F> lazy;

    // ノードの評価
    inline S eval(int k) const { return lazy[k] == oe ? node[k] : mapping(node[k], lazy[k]); }

    // 子に伝播
    inline void propagate(int k) {
        if(lazy[k] != oe) {
            lazy[2 * k] = composition(lazy[2 * k], lazy[k]);
            lazy[2 * k + 1] = composition(lazy[2 * k + 1], lazy[k]);
            node[k] = eval(k);
            lazy[k] = oe;
        }
    }

    // 上から伝播
    inline void thrust(int k) {
        for(int i = 31 - __builtin_clz(k); i > 0; i--) {
            if((k >> i) >= 1)
                propagate(k >> i);
        }
    }

    // 下から再計算
    inline void recalc(int k) {
        while(k > 1) {
            k >>= 1;
            node[k] = op(eval(2 * k), eval(2 * k + 1));
        }
    }

  public:
    void set(int k, const S &x) { node[k + n] = x; }

    void build() {
        for(int i = n - 1; i > 0; i--)
            node[i] = op(node[2 * i], node[2 * i + 1]);
    }

    // [L,R)区間作用
    void update(int L, int R, F x) {
        L += n, R += n;
        int L0 = L / (L & -L), R0 = R / (R & -R) - 1;
        thrust(L0);
        thrust(R0);
        while(L < R) {
            if(L & 1) {
                lazy[L] = composition(lazy[L], x);
                L++;
            }
            if(R & 1) {
                R--;
                lazy[R] = composition(lazy[R], x);
            }
            L >>= 1;
            R >>= 1;
        }
        recalc(L0);
        recalc(R0);
    }

    // [L,R)区間取得
    S query(int L, int R) {
        L += n, R += n;
        thrust(L / (L & -L));
        thrust(R / (R & -R) - 1);
        S vl = e, vr = e;
        while(L < R) {
            if(L & 1) {
                vl = op(vl, eval(L));
                L++;
            }
            if(R & 1) {
                R--;
                vr = op(eval(R), vr);
            }
            L >>= 1;
            R >>= 1;
        }
        return op(vl, vr);
    }

    S at(int k) { return query(k, k + 1); };

    // !!未verify!!
    int max_right(int l, function<bool(S)> f) {
        if(l == org_size)
            return org_size;
        l += n;
        thrust(l / (l & -l));
        S cum = e;
        do {
            while(l % 2 == 0)
                l >>= 1;
            if(!f(op(cum, node[l]))) {
                while(l < n) {
                    l = 2 * l;
                    if(f(op(cum, node[l]))) {
                        cum = op(cum, node[l]);
                        l++;
                    }
                }
                return l - n;
            }
            cum = op(cum, node[l]);
            l++;
        } while((l & -l) != l);
        return org_size;
    }

    // !!未verify!!
    int min_left(int r, function<bool(S)> f) {
        if(r == 0)
            return 0;
        r += n;
        thrust(r / (r & -r) - 1);
        S cum = e;
        do {
            r--;
            while(r > 1 && (r % 2))
                r >>= 1;
            if(!f(op(node[r], cum))) {
                while(r < n) {
                    r = 2 * r + 1;
                    if(f(op(node[r], cum))) {
                        cum = op(node[r], cum);
                        r--;
                    }
                }
                return r + 1 - n;
            }
            cum = op(node[r], cum);
        } while((r & (-r) != r));
        return 0;
    }

    LazySegTree(int sz, const Op op, const Mapping mapping,
                const Composition composition, const S &e, const F &oe)
        : op(op), mapping(mapping), composition(composition), e(e), oe(oe) {
        org_size = sz;
        n = 1;
        while(n < org_size) {
            n <<= 1;
        }
        node.resize(2 * n, e);
        lazy.resize(2 * n, oe);
    }
    LazySegTree(const vector<S> &v, const Op op, const Mapping mapping,
                const Composition composition, const S &e, const F &oe)
        : op(op), mapping(mapping), composition(composition), e(e), oe(oe) {
        org_size = v.size();
        n = 1;
        while(n < org_size) {
            n <<= 1;
        }
        node.resize(2 * n, e);
        lazy.resize(2 * n, oe);
        for(int i = 0; i < org_size; i++)
            set(i, v[i]);
        build();
    }
};
using S = int;
using F = int;
S e() { return int(1e9); }
F id() { return -1; }
S op(S a, S b) { return min(a, b); };
S mapping(S a, F f) { return a = id() ? f : a; };
F composition(F f, F g) { return f = id() ? g : f; };

void solve() {
    INT(n, Q);
    TVEC(int, l, r, b, Q);
    msort(b, l, r);
    LazySegTree<S, F> seg(n, op, mapping, composition, e(), id());
    rep(i, Q) {
        l[i]--;
        seg.update(l[i], r[i], b[i]);
    }

    vector<int> res(n);
    rep(i, n) res[i] = seg.at(i);
    rep(i, Q) {
        if(seg.query(l[i], r[i]) != b[i]) {
            write(-1);
            return;
        }
    }
    write(res);
}

int main() {

    int t = 1;
    // cin >> t;
    while(t--) {
        solve();
    }
}