#include <bits/stdc++.h>
using namespace std;
#define FOR(i, n) for(int i = 0; i < (n); i++)
#define MEM(a, x) memset(a, x, sizeof(a))
#define ALL(a) a.begin(), a.end()
#define UNIQUE(a) a.erase(unique(ALL(a)), a.end())
typedef long long ll;
typedef pair<int, int> P;

int gx, gy, n, f, dp[105][105];

int main(int argc, char const *argv[]) {
	ios_base::sync_with_stdio(false);
	cin >> gx >> gy >> n >> f;
	FOR(i, gx+1) FOR(j, gy+1) dp[i][j] = (i+j)*f;
	FOR(cnt, n) {
		int x, y, c;
		cin >> x >> y >> c;
		dp[x][y] = min(dp[x][y], c);
		for (int i = x; i <= gx; i++) {
			for (int j = y; j <= gy; j++) {
				dp[i][j] = min(dp[i-x][j-y]+dp[x][y], dp[i][j]);
			}
		}
	}
	cout << dp[gx][gy] << endl;
	return 0;
}