#include <bits/stdc++.h>
using namespace std;
// #include <ext/pb_ds/assoc_container.hpp>
// #include <ext/pb_ds/tree_policy.hpp>
// using namespace __gnu_pbds;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii ;
typedef pair<ll, ll> pll ;
typedef vector<pii> vii ;
typedef vector<int> veci ;
typedef vector<pll> vll ;
typedef vector<ll> vecll;
// find_by_order order_of_key
//#pragma GCC optimize("O3,unroll-loops")
//#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
#define ordered_set tree<int, null_type,less<int>, rb_tree_tag,tree_order_statistics_node_update>
#define F first
#define S second
#define pb push_back
#define endl '\n'
#define Mp make_pair
#define all(x) x.begin(), x.end()
#define debug(x) cerr << #x << " = " << x << endl
#define set_dec(x) cout << fixed << setprecision(x);
#define fast_io ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#define file_io freopen("in.txt" , "r" , stdin) ; freopen("out.txt" , "w" , stdout);
#define lb lower_bound
#define ub upper_bound
#define for1(n) for(int i=1;i<=n;i++)
#define for0(n) for(int i=0;i<n;i++)
#define forn(n) for(int i=n;i>0;i--)
#define pq priority_queue <pii, vector<pii>, greater<pii>>
const ll inf=1e18;
const int N=1<<17;
int n,m;
map<int,ll>seg[N*2],segg[N*2];
vector<int>vec;
pair<pii,pii>A[N];
void AD(int v,int rx,ll x){
auto it=seg[v].lb(rx+1);
if(it!=seg[v].begin()){
it--;
if((*it).S<=x)return;
}
seg[v][rx]=x;
while(1){
it=seg[v].ub(rx);
if(it==seg[v].end() || (*it).S<x)return;
seg[v].erase(it);
}
}
void ADD(int v,int lx,ll x){
auto it=segg[v].lb(lx);
if(it!=segg[v].end() && (*it).S<=x)return;
segg[v][lx]=x;
while((*segg[v].begin()).S!=x){
it=segg[v].find(lx);it--;
if((*it).S<x)return;
segg[v].erase(it);
}
}
void upd(int i,int rx,int lx,ll x,int l=0,int r=vec.size(),int v=1){
AD(v,rx,x);
ADD(v,lx,x);
if(r-l==1)return;
int mid=(l+r)>>1;
if(i<mid)upd(i,rx,lx,x,l,mid,v<<1);
else upd(i,rx,lx,x,mid,r,v<<1|1);
}
ll get(int i,int lxx,int rxx,int l=0,int r=vec.size(),int v=1){
if(r<=i){
auto it=seg[v].lb(lxx);
if(it==seg[v].end())return inf;
return (*it).S;
}
if(l>=i){
auto it=segg[v].lb(rxx+1);
if(it==segg[v].begin())return inf;
it--;
return (*it).S;
}
int mid=(l+r)>>1;
return min(get(i,lxx,rxx,l,mid,v<<1),get(i,lxx,rxx,mid,r,v<<1|1));
}
int main(){
fast_io
cin>>n>>m;
for1(m){cin>>A[i].S.F>>A[i].F.S>>A[i].F.F>>A[i].S.S;vec.pb(A[i].S.F);}
sort(all(vec));vec.resize(unique(all(vec))-vec.begin());
sort(A+1,A+m+1);
ll anss=inf;
for1(m){
int r=A[i].F.F,l=A[i].F.S,c=A[i].S.S,t=A[i].S.F;t=lb(all(vec),t)-vec.begin();
ll ans;
if(l==1)
ans=c;
else
ans=min(inf,get(t,vec[t]+l-1,-vec[t]+l+1)+c);
// cout<<l<<" "<<r<<" "<<t<<" "<<c<<":"<<ans<<endl;
if(r==n)anss=min(anss,ans);
else
upd(t,vec[t]+r,-vec[t]+r,ans);
}
cout<<anss<<endl;
}
