#include <stdio.h>

 #include <algorithm>

 #include <string.h>

 using namespace std;

 const int N =  + ;

 int n,m,r;

 struct node

 {

     int l,r,val;

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

 }p[N];

 int dp[N];

 int dfs(int u)

 {

     if(dp[u] != -) return dp[u];

     int ans = p[u].val;

     for(int i=;i<=m;i++)

     {

         if(p[u].r + r <= p[i].l)

         {

             ans = max(ans, p[u].val + dfs(i));

         }

     }

     return dp[u] = ans;

 }

 int main()

 {

     while(scanf("%d%d%d",&n,&m,&r) == )

     {

         for(int i=;i<=m;i++) p[i].read();

         memset(dp,-,sizeof dp);

         int ans = ;

         for(int i=;i<=m;i++) ans = max(ans, dfs(i));

         printf("%d\n",ans);

     }

     return ;

 }