#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
using P = pair<int, int>;

const int INF = 1 << 30;

template<
    class S, S (*op)(S, S), S(*e)(),
    class F, S (*mapping)(F, S), F (*composition)(F, F), F(*id)()> class LazySegTree{
private:
    int n;
    int h;
    vector<S> data;
    vector<F> lazy;

    void all_apply(int ind, F f){
        data[ind] = mapping(f, data[ind]);
        if(ind < n) lazy[ind] = composition(f, lazy[ind]);
    }

    void push(int ind){
        all_apply(ind<<1|0, lazy[ind]);
        all_apply(ind<<1|1, lazy[ind]);
        lazy[ind] = id();
    }

    void update(int ind){
        data[ind] = op(data[ind<<1|0], data[ind<<1|1]);
    }
public:
    LazySegTree(int sz){
        n = 1;
        h = 1;
        while(n < sz){
            n <<= 1;
            h++;
        }
        data = vector<S>(n*2, e());
        lazy = vector<F>(n, id());
    }

    void set(int ind, S x){
        ind += n;
        for(int lg = h-1; lg > 0; lg--) push(ind>>lg);
        data[ind] = x;
        for(int lg = 1; lg < h; lg++) update(ind>>lg);
    }

    S get(int ind){
        ind += n;
        for(int lg = h-1; lg > 0; lg--) push(ind>>lg);
        return data[ind];
    }

    S query(int l, int r){
        l += n; r += n;
        S lres = e(), rres = e();
        for(int lg = h-1; lg > 0; lg--){
            if(((l>>lg)<<lg) != l) push(l>>lg);
            if(((r>>lg)<<lg) != r) push((r-1)>>lg);
        }
        while(l < r){
            if(l&1){
                lres = op(lres, data[l]);
                l++;
            }
            if(r&1){
                r--;
                rres = op(data[r], rres);
            }
            l >>= 1;
            r >>= 1;
        }
        return op(lres, rres);
    }

    void apply(int ind, F f){
        ind += n;
        for(int lg = h-1; lg > 0; lg--) push(ind>>lg);

        data[ind] = mapping(f, data[ind]);

        for(int lg = 1; lg < h; lg++) update(ind>>lg);
    }

    void apply(int l, int r, F f){
        l += n; r += n;
        for(int lg = h-1; lg > 0; lg--){
            if(((l>>lg)<<lg) != l) push(l>>lg);
            if(((r>>lg)<<lg) != r) push((r-1)>>lg);
        }
        int l2 = l, r2 = r;
        while(l2 < r2){
            if(l2&1){
                all_apply(l2, f);
                l2++;
            }
            if(r2&1){
                r2--;
                all_apply(r2, f);
            }
            l2 >>= 1;
            r2 >>= 1;
        }
        for(int lg = 1; lg < h; lg++){
            // data[ind>>lg] = op(data[(ind>>lg)<<1|0], data[(ind>>lg)<<1|1]);
            if(((l>>lg)<<lg) != l) update(l>>lg);
            if(((r>>lg)<<lg) != r) update((r-1)>>lg);
        }
    }
};

int op(int x, int y){
    return min(x, y);
}

int e(){
    return INF;
}

int mapping(int f, int s){
    return (f == INF) ? s : f;
}

int composition(int f, int g){
    return (f == INF) ? g : f;
}

int id(){
    return INF;
}

int main(){
    int n, q; cin >> n >> q;
    vector<int> l(q), r(q), b(q);
    for(int i = 0; i < q; i++){
        cin >> l[i] >> r[i] >> b[i];
        l[i]--; r[i]--;
    }

    vector<P> mem(q);
    for(int i = 0; i < q; i++){
        mem[i].first = b[i];
        mem[i].second = i;
    }
    sort(mem.begin(), mem.end());

    LazySegTree<int, op, e, int, mapping, composition, id> st(n);
    st.apply(0, n, 1000000000);
    for(int i = 0; i < q; i++){
        st.apply(l[mem[i].second], r[mem[i].second]+1, mem[i].first);
    }

    // for(int i = 0; i < n; i++) cerr << st.get(i) << " ";
    // cerr << endl;

    bool isok = true;
    for(int i = 0; i < q; i++){
        if(st.query(l[i], r[i]+1) != b[i]) isok = false;
    }
    if(!isok){
        cout << -1 << endl;
    }else{
        for(int i = 0; i < n; i++){
            if(i != 0) cout << " ";
            cout << st.get(i);
        }
        cout << endl;
    }
    return 0;
}