#include <bits/stdc++.h>
#define rep(x, to) for (int x = 0; x < (to); x++)
#define REP(x, a, to) for (int x = (a); x < (to); x++)
#define EPS (1e-14)
#define _PA(x,N) rep(i,N){cout<<x[i]<<" ";}cout<<endl;
#define _PA2(x,H,W) rep(i,(H)){rep(j,(W)){cout<<x[i][j]<<" ";}cout<<endl;}

using namespace std;

typedef long long ll;
typedef pair<int, int> PII;
typedef pair<ll, ll> PLL;
typedef complex<double> Complex;
typedef vector< vector<int> > Mat;

const int INF = 1e+9 + 7;

int Gx, Gy;
int N, F;
int x[55], y[55], c[55];

int dp[55][105][105];

void solve() {
	for (int i = 0; i < 105; i++) {
		for (int j = 0; j < 105; j++) {
			dp[0][i][j] = F * i + F * j;
		}
	}
	for (int i = 0; i < N; i++) {
		for (int j = 0; j < 105; j++) { // y
			for (int k = 0; k < 105; k++) { // x
				dp[i+1][j][k] = dp[i][j][k];
				if (j-y[i] >= 0 && k-x[i] >= 0) {
					dp[i+1][j][k] = min(dp[i+1][j][k], dp[i][j-y[i]][k-x[i]] + c[i]);
				}
			}
		}
	}
	cout << dp[N][Gy][Gx] << endl;
#if 0
	rep(i, 5) {
		rep(j, 5) {
			rep(k, 5) {
				cout << dp[i][j][k] << " ";
			}
			cout << endl;
		}
		cout << endl;
	}
#endif
}

int main() {
	cin >> Gx >> Gy >> N >> F;
	rep(i, N) {
		cin >> x[i] >> y[i] >> c[i];
	}
	solve();
	return 0;
}