import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Arrays;

public class Main {

	static void solver() {
		int INF = Integer.MAX_VALUE / 4;
		int gx = ni();
		int gy = ni();
		int n = ni();
		int f = ni();
		int[] x = new int[n];
		int[] y = new int[n];
		int[] c = new int[n];
		for (int i = 0; i < n; i++) {
			x[i] = ni();
			y[i] = ni();
			c[i] = ni();
		}
		int[][] map = new int[101][101];
		for (int i = 0; i <= 100; i++) {
			for (int j = 0; j <= 100; j++) {
				map[i][j] = INF;
			}
		}
		map[0][0] = 0;
		long ans = f * (gx + gy);
		for (int i = 0; i < n; i++) {
			if (c[i] < (x[i] + y[i]) * f) {
				for (int sum = gx + gy; sum >= 0; sum--) {
					for (int xx = gx; xx >= 0; xx--) {
						int yy = sum - gx;
						if (yy < 0 || yy > gy)
							continue;
						if (map[xx][yy] != INF) {
							if (xx + x[i] <= gx && yy + y[i] <= gy) {
								map[xx + x[i]][yy + y[i]] = Math.min(map[xx][yy] + c[i], map[xx + x[i]][yy + y[i]]);
								ans = Math.min(ans, f * (gx + gy - xx - yy - x[i] - y[i]) + map[xx + x[i]][yy + y[i]]);
							}
						}
					}
				}
			} else {
				continue;
			}
		}
		out.println(ans);
	}
	static InputStream is;
	static PrintWriter out;
	static String INPUT = "";


	public static void main(String[] args) throws Exception
	{
		is = INPUT.isEmpty() ? System.in : new ByteArrayInputStream(INPUT.getBytes());
		out = new PrintWriter(System.out);

		solver();
		out.flush();
	}

	static long nl()
	{
		try {
			long num = 0;
			boolean minus = false;
			while((num = is.read()) != -1 && !((num >= '0' && num <= '9') || num == '-'));
			if(num == '-'){
				num = 0;
				minus = true;
			}else{
				num -= '0';
			}

			while(true){
				int b = is.read();
				if(b >= '0' && b <= '9'){
					num = num * 10 + (b - '0');
				}else{
					return minus ? -num : num;
				}
			}
		} catch (IOException e) {
		}
		return -1;
	}

	static char nc()
	{
		try {
			int b = skip();
			if(b == -1)return 0;
			return (char)b;
		} catch (IOException e) {
		}
		return 0;
	}

	static double nd()
	{
		try {
			return Double.parseDouble(ns());
		}catch(Exception e) {
		}
		return 0;
	}

	static String ns()
	{
		try{
			int b = skip();
			StringBuilder sb = new StringBuilder();
			if(b == -1)return "";
			sb.append((char)b);
			while(true){
				b = is.read();
				if(b == -1)return sb.toString();
				if(b <= ' ')return sb.toString();
				sb.append((char)b);
			}
		} catch (IOException e) {
		}
		return "";
	}

	public static char[] ns(int n)
	{
		char[] buf = new char[n];
		try{
			int b = skip(), p = 0;
			if(b == -1)return null;
			buf[p++] = (char)b;
			while(p < n){
				b = is.read();
				if(b == -1 || b <= ' ')break;
				buf[p++] = (char)b;
			}
			return Arrays.copyOf(buf, p);
		} catch (IOException e) {
		}
		return null;
	}

	public static byte[] nse(int n)
	{
		byte[] buf = new byte[n];
		try{
			int b = skip();
			if(b == -1)return null;
			is.read(buf);
			return buf;
		} catch (IOException e) {
		}
		return null;
	}

	static int skip() throws IOException
	{
		int b;
		while((b = is.read()) != -1 && !(b >= 33 && b <= 126));
		return b;
	}

	static boolean eof()
	{
		try {
			is.mark(1000);
			int b = skip();
			is.reset();
			return b == -1;
		} catch (IOException e) {
			return true;
		}
	}

	static int ni()
	{
		try {
			int num = 0;
			boolean minus = false;
			while((num = is.read()) != -1 && !((num >= '0' && num <= '9') || num == '-'));
			if(num == '-'){
				num = 0;
				minus = true;
			}else{
				num -= '0';
			}

			while(true){
				int b = is.read();
				if(b >= '0' && b <= '9'){
					num = num * 10 + (b - '0');
				}else{
					return minus ? -num : num;
				}
			}
		} catch (IOException e) {
		}
		return -1;
	}
}