#include <bits/stdc++.h>
using namespace std;
#define sz(x) (int) (x).size()
#define all(x) (x).begin(), (x).end()
#define show(x) cerr << #x << " is " << x << endl;
#define show2(x,y) cerr << #x << " is " << x << " " << #y << " is " << y << endl;
#define show3(x,y,z) cerr << #x << " is " << x << " " << #y << " is " << y << " " << #z << " is " << z << endl;
#define tern(cond, a, b) (cond ? a : b)
typedef long long lint;
typedef pair<int,int> ii;
struct thing{
lint t, l, r, c;
};
vector<thing> arr;
struct node{
lint s, e, m;
lint val = 10234567890123456;
node *l = nullptr, *r = nullptr;
node(int S, int E){
s = S, e = E, m = (s+e)/2;
}
inline void create(){
if(s != e and l == nullptr){
l = new node(s, m);
r = new node(m+1, e);
}
}
lint query(int S, int E){
create();
if(s == S and e == E) return val;
else if(E <= m) return l->query(S, E);
else if(S >= m+1) return r->query(S, E);
else return min(l->query(S, m), r->query(m+1, E));
}
void update(int P, lint X){
create();
if(s == e) val = min(X, val);
else{
if(P <= m) l->update(P, X);
else r->update(P, X);
val = min(l->val, r->val);
}
}
} *root = new node(0, 1000000005);
int main(){
ios_base::sync_with_stdio(false); cin.tie(0);
int L, n; cin >> L >> n;
for(int i = 0;i < n;i++){
int t, l, r, c; cin >> t >> l >> r >> c;
arr.push_back({t,l,r,c});
}
root->update(0,0);
sort(all(arr), [&](thing a, thing b){ return a.r < b.r; });
for(thing &t : arr){
lint dp = root->query(t.l-1, t.r) + t.c;
root->update(t.r, dp);
}
lint ans = root->query(L,L);
if(ans > 10232567890123456LL) ans = -1;
cout << ans;
}
