#include <iostream>
#include <cstdio>
#include <vector>
#include <algorithm>
#include <utility>

using namespace std;

const int inf = 1e9;

void show(vector<vector<int>> &vv) {
	cout << "------" << endl;
	for (auto v : vv) {
		for (auto e : v) {
			if (e == inf) {
				printf("inf ");
			} else {
				printf("%3d ", e);
			}
		}
		printf("\n");
	}
}

int main() {
	int gx, gy, n, f;
	cin >> gx >> gy >> n >> f;

	vector<vector<int>> board(gy + 1, vector<int>(gx + 1, inf));
	board[0][0] = 0;

	int x, y, c;
	for (int i = 0; i < n; i++) {
		cin >> x >> y >> c;
		if (c >= (x + y) * f) {
			continue;
		}

		for (int j = gy; j >= 0; j--) {
			for (int k = gx; k >= 0; k--) {
				if (board[j][k] == inf) {
					continue;
				}
				int nx = k + x;
				int ny = j + y;

				if (nx > gx || ny > gy) {
					continue;
				}
				board[ny][nx] = min(board[ny][nx], board[j][k] + c);
	// show(board);
			}
		}
	}

	// show(board);

	int ans = inf;
	for (int i = 0; i <= gy; i++) {
		for (int j = 0; j <= gx; j++) {
			ans = min(ans, (gy + gx - i - j) * f + board[i][j]);
		}
	}

	cout << ans << endl;
	return 0;
}