#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<algorithm>
#define N 100005
#define int long long
#define ul unsigned long long
#define db double
#define fo(i,l,r) for(int i=l;i<=r;i++)
#define rf(i,r,l) for(int i=r;i>=l;i--)
using namespace std;
int n,m,b[N<<1],t[N<<1],f[N],ans;
struct node{int k,w,l,r;bool operator<(node y){return k<y.k;}}a[N]; 
void swap(int &x,int &y){int t=x;x=y;y=t;}
int max(int x,int y){return x>y?x:y;}
int min(int x,int y){return x<y?x:y;}
void ud(int x,int k){while(x<=m)t[x]=max(t[x],k),x+=x&-x;}
int gs(int x){int sum=0;while(x)sum=max(sum,t[x]),x&=x-1;return sum;}
int read(){
	int sum=0;bool f=0;char c=getchar();
	for(;c<48||c>57;c=getchar())if(c==45)f=1;
	for(;c>=48&&c<=57;c=getchar())sum=sum*10+(c&15);
	return f?-sum:sum;
}
signed main(){
	freopen("power.in","r",stdin);freopen("power.out","w",stdout);
	n=read();read();
	fo(i,1,n)a[i]={read(),read(),b[i*2-1]=read(),b[i*2]=read()};
	sort(b+1,b+n+n+1);
	m=unique(b+1,b+n+n+1)-b-1;
	fo(i,1,n)a[i].l=lower_bound(b+1,b+m+1,a[i].l)-b,a[i].r=lower_bound(b+1,b+m+1,a[i].r)-b;
	sort(a+1,a+n+1);
	for(int i=1;i<=n;)
	{
		int j=i;
		for(;j<=n&&a[i].k==a[j].k;j++)
			f[j]=gs(a[j].l-1)+a[j].w;
		for(;i<j;i++)
			ud(a[i].r,f[i]); 
	}
	ans=0;fo(i,1,n)ans=max(ans,f[i]);
	printf("%lld",ans); 
	return 0;
}