#include <iostream>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <string>
#include <map>
#include <iomanip>
#include <algorithm>
#include <queue>
#include <stack>
#include <set>
#include <vector>
//const int maxn = 1e5+5;
#define ll long long
ll gcd(ll a,ll b){return b?gcd(b,a%b):a;}
ll lcm(ll a,ll b){return a/gcd(a,b)*b;}

#define MAX INT_MAX
#define FOR(i,a,b) for( int i = a;i <= b;++i)
#define bug cout<<"--------------"<<endl
using namespace std;
struct node
{
    int l,r,sum;
}a[1100];
int n,m,R;
int dp[1100];
bool cmp(node a,node b)
{
    if(a.l == b.l) return a.r < b.r;
    return a.l < b.l;
}
int main()
{
      ios::sync_with_stdio(false);
      cin>>n>>m>>R;
      FOR(i,1,m)
      {
          cin>>a[i].l>>a[i].r>>a[i].sum;
      }
      sort(a+1,a+1+m,cmp);
      for(int i=1;i<=m;++i)
      {
          dp[i] = a[i].sum;
          for(int j=1;j<i;++j)
          {
              dp[i] = max(dp[i], dp[j]);
              if(a[i].l >= a[j].r + R) dp[i] = max(dp[i], dp[j] + a[i].sum);
          }
      }
      cout<<dp[m]<<endl;
//      FOR(i,1,m)
//      cout<<dp[i]<<endl;

}