package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

func getScanner(fp *os.File) *bufio.Scanner {
	scanner := bufio.NewScanner(fp)
	scanner.Split(bufio.ScanWords)
	scanner.Buffer(make([]byte, 1000005), 1000005)
	return scanner
}
func getNextString(scanner *bufio.Scanner) string {
	scanner.Scan()
	return scanner.Text()
}
func getNextInt(scanner *bufio.Scanner) int {
	i, _ := strconv.Atoi(getNextString(scanner))
	return i
}
func getNextInt64(scanner *bufio.Scanner) int64 {
	i, _ := strconv.ParseInt(getNextString(scanner), 10, 64)
	return i
}
func getNextUint64(scanner *bufio.Scanner) uint64 {
	i, _ := strconv.ParseUint(getNextString(scanner), 10, 64)
	return i
}
func getNextFloat64(scanner *bufio.Scanner) float64 {
	i, _ := strconv.ParseFloat(getNextString(scanner), 64)
	return i
}
func main() {
	fp := os.Stdin
	wfp := os.Stdout
	cnt := 0
	if os.Getenv("MASPY") == "ますピ" {
		fp, _ = os.Open(os.Getenv("BEET_THE_HARMONY_OF_PERFECT"))
		cnt = 3
	}
	if os.Getenv("MASPYPY") == "ますピッピ" {
		wfp, _ = os.Create(os.Getenv("NGTKANA_IS_GENIUS10"))
	}
	scanner := getScanner(fp)
	writer := bufio.NewWriter(wfp)
	solve(scanner, writer)
	for i := 0; i < cnt; i++ {
		fmt.Fprintln(writer, "-----------------------------------")
		solve(scanner, writer)
	}
	writer.Flush()
}
func solve(scanner *bufio.Scanner, writer *bufio.Writer) {
	gx := getNextInt(scanner) + 1
	gy := getNextInt(scanner) + 1
	n := getNextInt(scanner)
	f := cint(getNextInt(scanner))
	xx := make([]int, n)
	yy := make([]int, n)
	cc := make([]cint, n)
	for i := 0; i < n; i++ {
		xx[i] = getNextInt(scanner)
		yy[i] = getNextInt(scanner)
		cc[i] = cint(getNextInt(scanner))
	}
	dp := makeGrid(gy, gx)
	for i := 0; i < gy; i++ {
		for j := 0; j < gx; j++ {
			if i+1 < gy {
				dp[i+1][j] = dp[i][j] + f
			}
			if j+1 < gx {
				dp[i][j+1] = dp[i][j] + f
			}
		}
	}
	dp[0][0] = 0
	for i := 0; i < n; i++ {
		for j := gy - 1; j >= 0; j-- {
			for k := gx - 1; k >= 0; k-- {
				if j-yy[i] >= 0 && k-xx[i] >= 0 {
					dp[j][k].min(dp[j-yy[i]][k-xx[i]] + cc[i])
				}
			}
		}
	}

	fmt.Fprintln(writer, dp[gy-1][gx-1])
}

func makeGrid(h, w int) [][]cint {
	index := make([][]cint, h, h)
	data := make([]cint, h*w, h*w)
	for i := 0; i < h; i++ {
		index[i] = data[i*w : (i+1)*w]
	}
	return index
}

type cint int

func (x *cint) min(y cint) *cint {
	if *x > y {
		*x = y
	}
	return x
}
func (x *cint) max(y cint) *cint {
	if *x < y {
		*x = y
	}
	return x
}