#include <iostream>
#include <vector>
#include <cmath>
using namespace std;



int main() {
    int level, k = 0;
    while (k == 0 || level == 0)
        cin >> level >> k;
    vector<int> monsters_on_level(level), time_level_start(level), time_level_finish(level);
    for (size_t i = 0; i < level; ++i)
        cin >> time_level_start[i] >> time_level_finish[i] >> monsters_on_level[i];
    vector<int> counter_bullet(level, INT_MAX);
    counter_bullet[0] = 0;

    int res = INT_MAX;
    for (size_t i = 0; i < level; ++i) {
        int left = k;
        int spend_bullets_level = counter_bullet[i];
        for (size_t j = i; j < level; ++j) {
            int count_reloads = max(0, (((monsters_on_level[j] - left) + k - 1) / k));
            if (count_reloads > time_level_finish[j] - time_level_start[j]) {
                break;
            }
            int new_left_bullet_magazine = left + k * count_reloads - monsters_on_level[j];
            if (spend_bullets_level != INT_MAX) {
                spend_bullets_level += monsters_on_level[j];
            }
            if (j + 1 < level) {
                if (time_level_start[j] + count_reloads < time_level_start[j + 1])
                    counter_bullet[j + 1] = min(counter_bullet[j + 1], spend_bullets_level == INT_MAX ? INT_MAX : spend_bullets_level + new_left_bullet_magazine);
            }
            else res = min(res, spend_bullets_level);
            left = new_left_bullet_magazine;
        }
    }
    res == INT_MAX ? cout << -1 : cout << res;
    return 0;
}