#include<iostream>

 #include<cstdio>

 #include<cstring>

 #include<algorithm>

 using namespace std;

 int max(int &a,int &b){return a>b?a:b;}

 struct data{

     int l,r,val;

     void Init(){scanf("%d%d%d",&l,&r,&val);}

     bool operator < (const data &tmp) const{

         return l<tmp.l;

     }

 }a[];

 int n,m,R,f[];

 int main(){

     scanf("%d%d%d",&n,&m,&R);

     for(int i=;i<=m;++i) a[i].Init();

     sort(a+,a+m+); int k=;

     for(int i=;i<=n+R;++i){

         if(i) f[i]=max(f[i],f[i-]);

         for(;a[k].l==i&&k<=m;++k)

             f[a[k].r+R]=max(f[a[k].r+R],f[i]+a[k].val);

     }printf("%d",f[n+R]);

     return ;

 }