#include <bits/stdc++.h>
using namespace std;
#define int long long
int memo[100005];
vector<pair<pair<int,int>,pair<int,int> > > stuff;
bool cmp(pair<pair<int,int>,pair<int,int>> a, pair<pair<int,int>,pair<int,int>> b){
return a.second.first-a.first.first<b.second.first-b.first.first;
}
int T[100005];
int L[100005];
int R[100005];
int C[100005];
int R_T[100005];
struct node{
int s,e,v;
node *l,*r;
node (int _s, int _e){
s = _s; e = _e;
v = 999999999999999999LL;
if (s!=e){
l = new node(s,(s+e)/2);
r = new node((s+e)/2+1,e);
}
}
void upd(int pos, int val){
if (s==e){
v = val;
return;
}
if (pos<=(s+e)/2) l->upd(pos,val);
else r->upd(pos,val);
v = min(l->v,r->v);
return ;
}
int qu(int a, int b){
if (a<=s && e<=b) return v;
if (b<=(s+e)/2) return l->qu(a,b);
if (a>(s+e)/2) return r->qu(a,b);
return min(l->qu(a,b),r->qu(a,b));
}
}*root;
main(){
int n,m;
scanf("%lld%lld",&n,&m);
root = new node(0,m);
for (int x = 0; x<m; x++){
int t,l,r,c;
scanf("%lld%lld%lld%lld",&t,&l,&r,&c);
stuff.push_back({{t,l},{r,c}});
}
sort(stuff.begin(),stuff.end(),cmp);
for (int x = 0; x<m; x++){
T[x] = stuff[x].first.first;
L[x] = stuff[x].first.second;
R[x] = stuff[x].second.first;
C[x] = stuff[x].second.second;
R_T[x] = R[x];
}
int ans = 999999999999999999LL;
for (int x = 0; x<m; x++){
if (L[x]==1){
memo[x] = C[x];
root->upd(x,C[x]);
continue;
}
memo[x] = C[x];
int minv = lower_bound(R_T,R_T+m,L[x]-1)-R_T;
memo[x] += root->qu(minv,x);
memo[x] = min(memo[x],999999999999999999LL);
root->upd(x,memo[x]);
}
for (int x = 0; x<m; x++){
if (R[x]==n){
ans = min(ans,memo[x]);
}
//printf("memo %lld = %lld\n",x,memo[x]);
}
printf("%lld",ans==999999999999999999LL?-1LL:ans);
}
