1 /*
  2 Source Code
  3 
  4 Problem: 3616  User: robinho364 
  5 Memory: 180K  Time: 0MS 
  6 Language: C++  Result: Accepted 
  7 */
  8 #define _USE_MATH_DEFINES
  9 
 10 #ifdef ONLINE_JUDGE
 11 #define FINPUT(file) 0
 12 #define FOUTPUT(file) 0
 13 #else
 14 #define FINPUT(file) freopen(file,"r",stdin)
 15 #define FOUTPUT(file) freopen(file,"w",stdout)
 16 #endif
 17 
 18 #include <iostream>
 19 #include <cstdio>
 20 #include <cstring>
 21 #include <cstdlib>
 22 #include <cmath>
 23 #include <ctime>
 24 #include <set>
 25 #include <stack>
 26 #include <string>
 27 #include <map>
 28 #include <vector>
 29 #include <queue>
 30 #include <algorithm>
 31 #include <functional>
 32 
 33 typedef long long ll;
 34 static const int M = 1010;
 35 static const int N = 1000010;
 36 static const int LEN = 1000010;
 37 static const int MAX = 0x7fffffff;
 38 static const int MIN = ~MAX;
 39 static const double EPS = 1e-7;
 40 
 41 struct cow_t {
 42     int start;
 43     int end;
 44     int efficiency;
 45 
 46     bool operator < (const struct cow_t& t) const {
 47         if (end < t.end) {
 48             return true;
 49         }
 50         else {
 51             return false;
 52         }
 53     }
 54 }cows[M];
 55 
 56 void solve(int n, int m, int r)
 57 {
 58     for (int i = 0; i < m; i++) {
 59         scanf("%d%d%d", &cows[i].start, &cows[i].end, &cows[i].efficiency);
 60     }
 61 
 62     std::sort(cows, cows + m);
 63 
 64     int pos[M];
 65 
 66     for (int i = 0; i < m; i++) {
 67         int idx = i - 1;
 68         while (idx >= 0) {
 69             if (cows[idx].end + r <= cows[i].start) {
 70                 pos[i] = idx;
 71                 break;
 72             }
 73             idx--;
 74         }
 75         if (idx == -1) {
 76             pos[i] = -1;
 77         }
 78     }
 79 
 80     int dp[M];
 81     memset(dp, 0, sizeof(dp));
 82 
 83     for (int i = 0; i < m; i++) {
 84         if (pos[i] == -1) {
 85             dp[i] = std::max(cows[i].efficiency, dp[i - 1]);
 86         }
 87         else {
 88             dp[i] = std::max(dp[pos[i]] + cows[i].efficiency, dp[i - 1]);
 89         }
 90     }
 91 
 92     printf("%d\n", dp[m - 1]);
 93 }
 94 
 95 int main()
 96 {
 97     FINPUT("in.txt");
 98     FOUTPUT("out.txt");
 99 
100     int n, m, r;
101     while (scanf("%d%d%d", &n, &m, &r) != EOF) {
102         solve(n, m, r);
103     }
104     return 0;
105 }