#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

struct S {
	int x, y, d;
	bool operator <(const S& s) const {
		return d > s.d;
	}
};

int dx[50];
int dy[50];
int c[50];
int dist[51][110][110];

const int INF = 1 << 25;
int main() {
	cin.tie(0);
	ios::sync_with_stdio(false);

	int gx, gy, N, F;
	cin >> gx >> gy >> N >> F;

	for(int i = 0; i < N; i++) {
		cin >> dx[i] >> dy[i] >> c[i];
	}

	fill((int*)begin(dist), (int*)end(dist), INF);
	dist[0][0][0] = 0;
	for(int i = 0; i < N; i++) {
		for(int y = 0; y <= gy; y++) {
			for(int x = 0; x <= gx; x++) {
				if(dist[i][y][x] == INF) continue;
				dist[i + 1][y][x] = min(dist[i + 1][y][x], dist[i][y][x]);
				int nx = x + dx[i], ny = y + dy[i];
				if(nx <= gx && ny <= gy) {
					dist[i + 1][ny][nx] = min(dist[i + 1][ny][nx], dist[i][y][x] + c[i]);
				}
			}
		}
	}

	int ans = INF;
	for(int y = 0; y <= gy; y++) {
		for(int x = 0; x <= gx; x++) {
			ans = min(ans, dist[N][y][x] + F * ((gx - x) + (gy - y)));

		}
	}
	cout << ans << endl;
}