#include "bits/stdc++.h"
#define _CRT_SECURE_NO_WARNINGS
#define rep(i,n) for(int i = 0;i < n;i++)
#define REP(i,n,k) for(int i = n;i < k;i++)
#define P(p) cout << (p) << endl;
#define sP(p) cout << setprecision(15) << fixed << p << endl;
#define vi vector<int>
#define mp(a,b) make_pair(a,b)
using namespace std;typedef long long ll;typedef unsigned long long ull;int dx[] = { 1, -1 , 0 , 0};int dy[] = { 0,  0,  1, -1};

void solve() {
	int dp[111][111];
	int gx, gy, n, f;
	cin >> gx >> gy >> n >> f;
	rep(i, 111)rep(j, 111) {
		dp[i][j] = (i + j)*f;
	}
	rep(i, n) {
		int x, y, c;
		cin >> x >> y >> c;
		for (int j = gx; j - x >= 0; j--) {
			for (int k = gy; k - y >= 0; k--) {
				dp[j][k] = min(dp[j][k], dp[j - x][k - y] + c);
			}
		}
	}
	P(dp[gx][gy]);
}

int main() {
	solve();
	return 0;
}