This documentation is automatically generated by competitive-verifier/competitive-verifier
// competitive-verifier: IGNORE
// competitive-verifier: PROBLEM https://atcoder.jp/contests/nikkeiqual_2019/tasks/nikkei2019_2_qual_d
// competitive-verifier: TLE 0.5
// competitive-verifier: MLE 256
// https://atcoder.jp/contests/nikkei2019-2-qual/tasks/nikkei2019_2_qual_d
#include <iostream>
#include <vector>
#include <algorithm>
#include <queue>
#include "src/Graph/RangeToRangeGraph.hpp"
using namespace std;
signed main() {
cin.tie(0);
ios::sync_with_stdio(0);
int N, M;
cin >> N >> M;
RangeToRangeGraph<int> r2r(N);
for (int i= 0; i < M; ++i) {
int L, R, C;
cin >> L >> R >> C;
--L;
r2r.add_from_range_to_range(L, R, L, R, C);
}
int n= r2r.graph.vertex_size();
auto adj= r2r.graph.adjacency_edge(1);
long long dist[n];
static constexpr long long INF= 1ll << 60;
fill_n(dist, n, INF);
priority_queue<pair<long long, int>> pq;
pq.emplace(0, 0);
dist[0]= 0;
while (!pq.empty()) {
auto [d, v]= pq.top();
pq.pop();
if (-d != dist[v]) continue;
for (auto e: adj[v]) {
int u= r2r.graph[e].to(v);
int w= r2r.weight[e];
long long cost= dist[v] + w;
if (dist[u] > cost) {
dist[u]= cost;
pq.emplace(-cost, u);
}
}
}
cout << (dist[N - 1] == INF ? -1 : dist[N - 1]) << '\n';
return 0;
}
#line 1 "test/atcoder/nikkei2019_2_qual_d.test.cpp"
// competitive-verifier: IGNORE
// competitive-verifier: PROBLEM https://atcoder.jp/contests/nikkeiqual_2019/tasks/nikkei2019_2_qual_d
// competitive-verifier: TLE 0.5
// competitive-verifier: MLE 256
// https://atcoder.jp/contests/nikkei2019-2-qual/tasks/nikkei2019_2_qual_d
#include <iostream>
#include <vector>
#include <algorithm>
#include <queue>
#line 4 "src/Internal/ListRange.hpp"
#include <iterator>
#include <type_traits>
#define _LR(name, IT, CT) \
template <class T> struct name { \
using Iterator= typename std::vector<T>::IT; \
Iterator bg, ed; \
Iterator begin() const { return bg; } \
Iterator end() const { return ed; } \
size_t size() const { return std::distance(bg, ed); } \
CT &operator[](int i) const { return bg[i]; } \
}
_LR(ListRange, iterator, T);
_LR(ConstListRange, const_iterator, const T);
#undef _LR
template <class T> struct CSRArray {
std::vector<T> dat;
std::vector<int> p;
size_t size() const { return p.size() - 1; }
ListRange<T> operator[](int i) { return {dat.begin() + p[i], dat.begin() + p[i + 1]}; }
ConstListRange<T> operator[](int i) const { return {dat.cbegin() + p[i], dat.cbegin() + p[i + 1]}; }
};
template <template <class> class F, class T> std::enable_if_t<std::disjunction_v<std::is_same<F<T>, ListRange<T>>, std::is_same<F<T>, ConstListRange<T>>, std::is_same<F<T>, CSRArray<T>>>, std::ostream &> operator<<(std::ostream &os, const F<T> &r) {
os << '[';
for (int _= 0, __= r.size(); _ < __; ++_) os << (_ ? ", " : "") << r[_];
return os << ']';
}
#line 3 "src/Graph/Graph.hpp"
struct Edge: std::pair<int, int> {
using std::pair<int, int>::pair;
Edge &operator--() { return --first, --second, *this; }
int to(int v) const { return first ^ second ^ v; }
friend std::istream &operator>>(std::istream &is, Edge &e) { return is >> e.first >> e.second, is; }
};
struct Graph: std::vector<Edge> {
size_t n;
Graph(size_t n= 0, size_t m= 0): vector(m), n(n) {}
size_t vertex_size() const { return n; }
size_t edge_size() const { return size(); }
size_t add_vertex() { return n++; }
size_t add_edge(int s, int d) { return emplace_back(s, d), size() - 1; }
size_t add_edge(Edge e) { return emplace_back(e), size() - 1; }
#define _ADJ_FOR(a, b) \
for (auto [u, v]: *this) a; \
for (size_t i= 0; i < n; ++i) p[i + 1]+= p[i]; \
for (int i= size(); i--;) { \
auto [u, v]= (*this)[i]; \
b; \
}
#define _ADJ(a, b) \
vector<int> p(n + 1), c(size() << !dir); \
if (!dir) { \
_ADJ_FOR((++p[u], ++p[v]), (c[--p[u]]= a, c[--p[v]]= b)) \
} else if (dir > 0) { \
_ADJ_FOR(++p[u], c[--p[u]]= a) \
} else { \
_ADJ_FOR(++p[v], c[--p[v]]= b) \
} \
return {c, p}
CSRArray<int> adjacency_vertex(int dir) const { _ADJ(v, u); }
CSRArray<int> adjacency_edge(int dir) const { _ADJ(i, i); }
#undef _ADJ
#undef _ADJ_FOR
};
#line 3 "src/Graph/RangeToRangeGraph.hpp"
template <typename cost_t= int> class RangeToRangeGraph {
int n;
inline int to_upper_idx(int i) const { return i >= n ? i - n : n + i; }
inline int to_lower_idx(int i) const { return i >= n ? i - n : n + n + i; }
public:
Graph graph;
std::vector<cost_t> weight;
RangeToRangeGraph(int n): n(n), graph(n * 3) {
for (int i= 2; i < n + n; ++i) add(to_upper_idx(i / 2), to_upper_idx(i));
for (int i= 2; i < n + n; ++i) add(to_lower_idx(i), to_lower_idx(i / 2));
}
void add(int s, int t, cost_t w= 0) { graph.add_edge(s, t), weight.emplace_back(w); }
// [s_l, s_r) -> t
void add_from_range(int s_l, int s_r, int t, cost_t w= 0) {
for (int l= s_l + n, r= s_r + n; l < r; l>>= 1, r>>= 1) {
if (l & 1) add(to_lower_idx(l++), t, w);
if (r & 1) add(to_lower_idx(--r), t, w);
}
}
// s -> [t_l, t_r)
void add_to_range(int s, int t_l, int t_r, cost_t w= 0) {
for (int l= t_l + n, r= t_r + n; l < r; l>>= 1, r>>= 1) {
if (l & 1) add(s, to_upper_idx(l++), w);
if (r & 1) add(s, to_upper_idx(--r), w);
}
}
// [s_l, s_r) -> [t_l, t_r)
void add_from_range_to_range(int s_l, int s_r, int t_l, int t_r, cost_t w= 0) { add_from_range(s_l, s_r, graph.n, w), add_to_range(graph.n, t_l, t_r, 0), ++graph.n; }
};
#line 11 "test/atcoder/nikkei2019_2_qual_d.test.cpp"
using namespace std;
signed main() {
cin.tie(0);
ios::sync_with_stdio(0);
int N, M;
cin >> N >> M;
RangeToRangeGraph<int> r2r(N);
for (int i= 0; i < M; ++i) {
int L, R, C;
cin >> L >> R >> C;
--L;
r2r.add_from_range_to_range(L, R, L, R, C);
}
int n= r2r.graph.vertex_size();
auto adj= r2r.graph.adjacency_edge(1);
long long dist[n];
static constexpr long long INF= 1ll << 60;
fill_n(dist, n, INF);
priority_queue<pair<long long, int>> pq;
pq.emplace(0, 0);
dist[0]= 0;
while (!pq.empty()) {
auto [d, v]= pq.top();
pq.pop();
if (-d != dist[v]) continue;
for (auto e: adj[v]) {
int u= r2r.graph[e].to(v);
int w= r2r.weight[e];
long long cost= dist[v] + w;
if (dist[u] > cost) {
dist[u]= cost;
pq.emplace(-cost, u);
}
}
}
cout << (dist[N - 1] == INF ? -1 : dist[N - 1]) << '\n';
return 0;
}