#include <bits/stdc++.h>

using namespace std;

typedef tuple<int, int, int> T;

const int INF = 1e8;

int main() {
	cin.tie(0);
	ios::sync_with_stdio(false);
	int gx, gy, n, f;
	cin >> gx >> gy >> n >> f;
	vector<int> x(n), y(n), c(n);
	for (int i = 0; i < n; i++) cin >> x[i] >> y[i] >> c[i];
	vector< vector<int> > d(gx + 1, vector<int>(gy + 1, INF));
	priority_queue<T, vector<T>, greater<T> > pq;
	pq.push(T(0, 0, 0));
	while (!pq.empty()) {
		int cost, w, h;
		tie(cost, w, h) = pq.top();
		pq.pop();
		if (d[w][h] <= cost) continue;
		d[w][h] = cost;
		if (w == gx && h == gy) break;
		if (w < gx && d[w + 1][h] > cost + f) pq.push(T(cost + f, w + 1, h));
		if (h < gy && d[w][h + 1] > cost + f) pq.push(T(cost + f, w, h + 1));
		for (int i = 0; i < n; i++) {
			int nw = w + x[i], nh = h + y[i];
			if (nw > gx || nh > gy) continue;
			if (d[nw][nh] > cost + c[i]) pq.push(T(cost + c[i], nw, nh));
		}
	}
	cout << d[gx][gy] << endl;
	return 0;
}