#include<iostream>
#include<cstdio>
#include<cctype>
#include<algorithm>
using namespace std;
inline void in(int &x){
    x=0;int f=1;char t=getchar();
    while(!isdigit(t)){if(t=='-')f=-1;t=getchar();}
    while(isdigit(t)){x=x*10+t-48;t=getchar();}
    x*=f;
}
const int maxm=1002;
int n,m,r;
struct timetable{
	int s,e,w;
}a[maxm];
inline bool cmp(timetable a,timetable b){
	return a.e<b.e;
}
int f[maxm];
inline void dpwork(){
	a[0].e=-r;
	for(int i=1;i<=m;i++){
		f[i]=f[i-1];
		for(int j=0;j<i;j++){
			if(a[j].e+r<=a[i].s) f[i]=max(f[i],f[j]+a[i].w);
		}
	}
	printf("%d",f[m]);
}
inline void work(){
	in(n);in(m);in(r);
	for(int i=1;i<=m;i++){
		in(a[i].s);in(a[i].e);in(a[i].w);
	}
	sort(a+1,a+m+1,cmp);
	dpwork();
}
inline int mian(){
    freopen("milkprod.in","r",stdin);
	freopen("milkprod.out","w",stdout);
	work();
}
int miku=mian();
int main(){;}