#include <stdio.h>

#include <stdlib.h>

#define maxm 1000

typedef struct interval {

int start, end;

int eff;

} interval;

int compare(const void *a, const void *b) {

return ((interval *)a)->end - ((interval *)b)->end;

}

interval ins[maxm];

int dp[maxm];

int max(int a, int b) {

return a > b ? a : b;

}

int main() {

int n, m, r;

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

for (int i = 0; i < m; i++) {

scanf("%d %d %d", &ins[i].start, &ins[i].end, &ins[i].eff);

}

qsort(ins, m, sizeof(interval), compare);

dp[0] = ins[0].eff;

int left, right, mid, k;

for (int i = 1; i < m; i++) {

//binary search

left = 0, right = i;

k = -1;

while (left <= right) {

mid = (left + right) >> 1;

if (ins[mid].end <= ins[i].start - r) {

k = mid;

left = mid + 1;

}

else right = mid - 1;

}

//DP

dp[i] = max(dp[i - 1], (k != -1 ? dp[k] : 0) + ins[i].eff);

}

printf("%d\n", dp[m - 1]);

exit(0);

}