import java.util.*;
import java.io.*;
public class Main {
    static int N = 1010;
    static long INF = Long.MAX_VALUE / 10;
    static long f[][] = new long[N][N]; // 

    static int a[][] = new int[N][3]; // a[i][1]：green lamb a[i][2]:red lamb
    static int n, m, k, v;

    static long get(long t, int p) {
        if(p == m)
            return 0;
        long lun = a[p][1] + a[p][2];
        t %= lun;
        return t >= a[p][1] ? lun - t : 0;
    }

    static long getRange(long t, int l, int r) {
        for(int i = l + 1; i <= r; i ++ ) {
            t += (a[i][0] - a[i - 1][0]) * v;
            t += get(t, i);
        }
        return t;
    }

    public static void main(String[] args) {
        IR sc = new IR();
        n = sc.nextInt();
        m = sc.nextInt();
        k = sc.nextInt();
        v = sc.nextInt();
        for(int i = 1; i <= m; i ++ ) {
            for(int j = 0; j < 3; j ++ ) {
                a[i][j] = sc.nextInt();
            }
        }
        Arrays.sort(a, 1, m + 1, (o1, o2) -> o1[0] - o2[0]);
        a[ ++ m][0] = n; 
        for(int i = 1; i <= m; i ++ ) {
            for(int j = 0; j <= i; j ++ ) {
                f[i][j] = INF;

                // 这次不用
                long tem = f[i - 1][j] + (a[i][0] - a[i - 1][0]) * v;
                f[i][j] = tem + get(tem, i);

                // 这次用
                if(j == 1) {
                    f[i][j] = Math.min(f[i][j], f[i - 1][j - 1] + get(f[i - 1][j - 1], i));
                } else if(j > 1){
                    if(i - k > 0) {
                        f[i][j] = Math.min(f[i][j], f[i - k][j - 1] + getRange(f[i - k][j - 1], i - k, i - 1));
                    }
                }
            }
            for(int j = i + 1; j <= m; j ++ )
                f[i][j] = INF;
        }
        long res = INF;
        for(int i = 0; i <= m; i ++ ) {
            res = Math.min(res, f[m][i]);
        }
        System.out.println(res);
    }
}


class IR {
    BufferedReader br;
    StringTokenizer st;

    IR() {
        br = new BufferedReader(new InputStreamReader(System.in));
    }

    boolean hasNext() {
        while(st == null || !st.hasMoreElements()) {
            try {
                st = new StringTokenizer(br.readLine());
            } catch (IOException e) {
                // TODO Auto-generated catch block
                return false;
            }
        }
        return true;
    }

    String next() {
        if(hasNext()) 
            return st.nextToken();
        return null;
    }

    int nextInt() {
        return Integer.parseInt(next());
    }

}