#include <bits/stdc++.h>
    using namespace std;
    #include <math.h>
    #include <iomanip>
    #include <cstdint>
    #include <string>
    #include <sstream>
    template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
    template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
    #define rep(i,n) for (int i = 0; i < (n); ++i)
    typedef long long ll;
    typedef unsigned long long ull;
    using P=pair<ll,ll>;
    const ll INF=1e9;
    const int mod=1e9+7;
    
struct LazySegmentTree {
private:
    int n;
    vector<int> node, lazy;
    vector<bool> lazyFlag;

public:
    LazySegmentTree(vector<int> v) {
        int sz = (int)v.size();
        n = 1; while(n < sz) n *= 2;
        node.resize(2*n-1);
        lazy.resize(2*n-1, INF);
        lazyFlag.resize(2*n-1, false);

        for(int i=0; i<sz; i++) node[i+n-1] = v[i];
        for(int i=n-2; i>=0; i--) node[i] = min(node[i*2+1], node[i*2+2]);
    }

    void lazyEvaluate(int k, int l, int r) {
        if(lazyFlag[k]) {
            node[k] = lazy[k];
            if(r - l > 1) {
                lazy[k*2+1] = lazy[k*2+2] = lazy[k];
                lazyFlag[k*2+1] = lazyFlag[k*2+2] = true;
            }
            lazyFlag[k] = false;
        }
    }

    void update(int a, int b, int x, int k=0, int l=0, int r=-1) {
        if(r < 0) r = n;
        lazyEvaluate(k, l, r);
        if(b <= l || r <= a) return;
        if(a <= l && r <= b) {
            lazy[k] = x;
            lazyFlag[k] = true;
            lazyEvaluate(k, l, r);
        }
        else {
            update(a, b, x, 2*k+1, l, (l+r)/2);
            update(a, b, x, 2*k+2, (l+r)/2, r);
            node[k] = min(node[2*k+1], node[2*k+2]);
        }
    }

    int find(int a, int b, int k=0, int l=0, int r=-1) {
        if(r < 0) r = n;
        lazyEvaluate(k, l, r);
        if(b <= l || r <= a) return INF;
        if(a <= l && r <= b) return node[k];
        int vl = find(a, b, 2*k+1, l, (l+r)/2);
        int vr = find(a, b, 2*k+2, (l+r)/2, r);
        return min(vl, vr);
    }
};

    void solve(){
        int n,q;
        cin>>n>>q;
        vector<vector<int>>tp(q,vector<int>(3));
        rep(i,q){
            int l,r,b;
            cin>>l>>r>>b;
            tp[i]={b,l,r};
        }
        sort(tp.begin(),tp.end());
        LazySegmentTree seg(vector<int>(n,INF));
        rep(i,q){
            int b=tp[i][0],l=tp[i][1],r=tp[i][2];
            l--;
            seg.update(l,r,b);
        }
        rep(i,q){
            int b=tp[i][0],l=tp[i][1],r=tp[i][2];
            l--;
            if(seg.find(l,r)!=b){
                cout<<-1<<endl;
                return;
            }
        }
        rep(i,n){
            if(i){cout<<" ";}
            cout<<seg.find(i,i+1);
        }
        cout<<endl;
    }
 
    int main(){
        ios_base::sync_with_stdio(false);
        cin.tie(NULL);
        
        solve(); 

        return 0;
    }