/* -*- coding: utf-8 -*-
 *
 * 496.cc: No.496 ワープクリスタル (給料日前編) - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int MAX_N = 50;
const int MAX_X = 100, MAX_Y = 100;
const int INF = 1 << 30;

/* typedef */

/* global variables */

int cxs[MAX_N], cys[MAX_N], cs[MAX_N];
int dp[MAX_Y + 1][MAX_X + 1];

/* subroutines */

inline void setmin(int &a, int b) { if (a > b) a = b; }

/* main */

int main() {
  int gx, gy, n, f;
  cin >> gx >> gy >> n >> f;
  for (int i = 0; i < n; i++) cin >> cxs[i] >> cys[i] >> cs[i];

  for (int y = 0; y <= gy; y++)
    for (int x = 0; x <= gx; x++) dp[y][x] = INF;
  dp[0][0] = 0;

  for (int i = 0; i < n; i++)
    for (int y = 0; y <= gy; y++)
      for (int x = 0; x <= gx; x++) {
	int &d0 = dp[y][x];
	if (d0 < INF) {
	  int x1 = x + cxs[i], y1 = y + cys[i];
	  if (x1 <= gx && y1 <= gy) setmin(dp[y1][x1], d0 + cs[i]);
	}
      }

  int minc = INF;
  for (int y = 0; y <= gy; y++)
    for (int x = 0; x <= gx; x++)
      if (dp[y][x] < INF)
	setmin(minc, dp[y][x] + ((gx - x) + (gy - y)) * f);
  printf("%d\n", minc);
  return 0;
}