#include<bits/stdc++.h>
using namespace std ;
#define maxn 300009
#define ll long long
#define fi first
#define se second
#define pb push_back
#define left id<<1
#define right id<<1|1
#define re exit(0);
#define _lower(v,x) lower_bound(v.begin(),v.end(),x)-v.begin()+1
const int mod = 1e9+7 ;
const int INF = 1e9 ;
const int LOG = 18 ;
typedef vector<int> vi ;
typedef pair<int,int> pii ;
typedef vector<pii> vii ;
typedef vector<ll> vl ;
typedef pair<ll,ll> pll ;
typedef vector<pll> vll ;
void add ( int&a , int b ) { if ((a+=b) > mod ) a -= mod ; }
void sub ( int&a , int b ) { if ((a-=b) < 0 ) a += mod ; }
template<typename T> void chkmin(T& x, T y) {if(x > y) x = y;}
template<typename T> void chkmax(T& x, T y) {if(x < y) x = y;}
void rf ( )
{
freopen ("bai1.inp","r",stdin) ;
// freopen ("bai1.out","w",stdout) ;
}
int _pow ( int a , int n )
{
if ( n == 0 ) return 1 ;
int res = _pow ( a , n / 2 ) ;
if ( n % 2 ) return ( 1ll * res * res % mod * a % mod ) ;
else return ( 1ll * res * res % mod ) ;
}
int n , m ;
struct project {
int t , l , r , c ;
} a[maxn];
struct dat {
int l , r , c ;
};
vector <dat> vec ;
int map_n ;
void mapping ()
{
vi v ;
v . pb (n) ;
v . pb (1) ;
for ( int i = 1 ; i <= m ; i ++ ) v . pb (a[i].l) , v . pb (a[i].r) , v . pb (a[i].r+1);
sort (v.begin(),v.end()) ;
v.resize (unique(v.begin(),v.end())-v.begin()) ;
for ( auto &x : vec ) x.l = _lower(v,x.l) , x.r = _lower(v,x.r) ;
map_n = _lower (v,n) ;
}
const int N = 3e5 ;
const int maxN = 3e5+9 ;
ll bit [maxN] ;
void clear_bit ()
{
for ( int i = 1 ; i <= map_n ; i ++ ) bit [i] = 1e18 ;
}
void update ( int x , ll y )
{
while ( x ) chkmin (bit[x],y) , x -= (x&-x) ;
}
ll get ( int x )
{
if ( ! x ) return 0 ;
ll res = 1e18 ;
while ( x <= map_n ) chkmin (res,bit[x]) , x += (x&-x) ;
return res ;
}
bool cmp_vec ( dat u , dat v )
{
return u.l < v.l ;
}
void sub1 ()
{
set <int> S;
ll res = 1e18 ;
for ( int i = 1 ; i <= m ; i ++ ) S . insert (a[i].t) ;
for ( auto TIME : S )
{
vec.clear() ;
for ( int i = 1 ; i <= m ; i ++ )
{
if ( a[i].t <= TIME )
{
int l = a[i].l , r = a[i].r ;
if ( l != 1 ) l += TIME - a[i].t ;
if ( r != n ) r -= TIME - a[i].t ;
if ( l <= r ) vec . pb ({l,r,a[i].c}) ;
}
}
mapping () ;
clear_bit () ;
sort (vec.begin(),vec.end(),cmp_vec) ;
for ( auto x : vec )
{
ll dp = get (x.l-1) + x.c ;
update (x.r,dp) ;
}
chkmin (res,get(map_n)) ;
}
if ( res == 1e18 ) res = - 1 ;
cout << res ;
}
// dp [i] la hoanh thanh den i
// dp [i] = dp [j-1] + cost (i,j)
int main ( )
{
ios_base :: sync_with_stdio (0) ;
cin.tie(0) ; cout.tie(0) ;
// rf () ;
cin >> n >> m ;
for ( int i = 1 ; i <= m ; i ++ ) cin >> a[i].t >> a[i].l >> a[i].r >> a[i].c ;
sub1 () ;
}
//-std=c++11
// range , time , error , stay hard stay hard
// there is no tomorrow
