#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N = 400'000;
const ll INF = 1'000'000'000'000'000'000;
int n, m, t[N + 10], l[N + 10], r[N + 10], c[N + 10];
ll seg[4 * N + 10], lazy[4 * N + 10];
int x;
vector<int> en[N + 10];
vector<int> vec;
void readInput() {
cin >> n >> m;
for (int i = 1; i <= m; i++)
cin >> t[i] >> l[i] >> r[i] >> c[i];
}
bool isSub1() {
return *max_element(t + 1, t + m + 1) == 1;
}
ll get(int idx, int id = 1, int l = 0, int r = x) {
if (idx < l || r <= idx)
return INF;
if (l + 1 == r)
return lazy[id];
int mid = (l + r) >> 1;
return min({lazy[id], get(idx, id << 1, l, mid), get(idx, id << 1 | 1, mid, r)});
}
void update(int st, int en, ll val, int id = 1, int l = 0, int r = x) {
if (en <= l || r <= st)
return;
if (st <= l && r <= en) {
lazy[id] = min(lazy[id], val);
return;
}
int mid = (l + r) >> 1;
update(st, en, val, id << 1, l, mid);
update(st, en, val, id << 1 | 1, mid, r);
}
void build(int id = 1, int l = 0, int r = x) {
for (int i = 1; i <= 4 * x + 5; i++)
lazy[i] = INF;
}
int getIdx(int x) {
return lower_bound(vec.begin(), vec.end(), x) - vec.begin();
}
void init() {
vec = {0, n};
for (int i = 1; i <= m; i++) {
vec.push_back(l[i]);
vec.push_back(r[i]);
}
sort(vec.begin(), vec.end());
vec.resize(unique(vec.begin(), vec.end()) - vec.begin());
for (int i = 1; i <= m; i++) {
l[i] = getIdx(l[i]);
r[i] = getIdx(r[i]);
en[r[i]].push_back(i);
}
x = vec.size();
}
void solveSub1() {
init();
build();
update(0, 1, 0);
for (int i = 1; i < x; i++) {
for (auto idx: en[i]) {
ll tmp = get(l[idx] - 1);
update(l[idx], i + 1, tmp + c[idx]);
}
}
ll ans = get(x - 1);
cout << (ans == INF? -1: ans) << flush;
}
void solveSub2() {
}
int main() {
ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
readInput();
if (isSub1())
solveSub1();
else if (m <= 16)
solveSub2();
return 0;
}
