#include <bits/stdc++.h>

using namespace std;

#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()

template<typename A, typename B> inline bool chmax(A &a, B b) { if (a<b) { a=b; return 1; } return 0; }
template<typename A, typename B> inline bool chmin(A &a, B b) { if (a>b) { a=b; return 1; } return 0; }

typedef unsigned long long ull;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

const ll INF = 1ll<<29;
const ll MOD = 1000000007;
const double EPS  = 1e-10;

int gx, gy, n, f;
int x[50], y[50], c[50];
int dp[101][101];

int main() {
	cin >> gx >> gy >> n >> f;
	REP(i, n) scanf("%d %d %d", x + i, y + i, c + i);
	
	fill(dp[0], dp[101], INF);
	
	dp[0][0] = 0;
	
	REP(i, gy + 1) REP(j, gx + 1) {
		if (i > 0) chmin(dp[i][j], dp[i - 1][j] + f);
		if (j > 0) chmin(dp[i][j], dp[i][j - 1] + f);
	}
	
	REP(t, n) {
		for (int i = gy; i >= y[t]; i--) {
			for (int j = gx; j >= x[t]; j--) {
				chmin(dp[i][j], dp[i - y[t]][j - x[t]] + c[t]);
			}
		}
	}
	
	cout << dp[gy][gx] << endl;
	
	return 0;
}