#include <iostream>
#include <string>
#include <queue>
#include <stack>
#include <algorithm>
#include <list>
#include <vector>
#include <complex>
#include <utility>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <climits>
#include <bitset>
#include <ctime>
#include <map>
#include <unordered_map>
#include <set>
#include <unordered_set>
#include <cassert>
#include <cstddef>
#include <iomanip>
#include <numeric>
#include <tuple>
#include <sstream>
#include <fstream>
#include <chrono>

using namespace std;
#define REP(i, n) for (int (i) = 0; (i) < (n); (i)++)
#define FOR(i, a, b) for (int (i) = (a); (i) < (b); (i)++)
#define RREP(i, a) for(int (i) = (a) - 1; (i) >= 0; (i)--)
#define FORR(i, a, b) for(int (i) = (a) - 1; (i) >= (b); (i)--)
#define DEBUG(C) cerr << #C << " = " << C << endl;
using LL = long long;
using VI = vector<int>;
using VVI = vector<VI>;
using VL = vector<LL>;
using VVL = vector<VL>;
using VD = vector<double>;
using VVD = vector<VD>;
using PII = pair<int, int>;
using PDD = pair<double, double>;
using PLL = pair<LL, LL>;
using VPII = vector<PII>;
template<typename T> using VT = vector<T>;
#define ALL(a) begin((a)), end((a))
#define RALL(a) rbegin((a)), rend((a))
#define SORT(a) sort(ALL((a)))
#define RSORT(a) sort(RALL((a)))
#define REVERSE(a) reverse(ALL((a)))
#define MP make_pair
#define FORE(a, b) for (auto &&a : (b))
#define FIND(s, e) ((s).find(e) != (s).end())
#define EB emplace_back
template<typename T>inline bool chmax(T &a, T b){return (a < b ? a = b, true : false);}
template<typename T>inline bool chmin(T &a, T b){return (a > b ? a = b, true : false);}

const int INF = 1e9;
const int MOD = INF + 7;
const LL LLINF = 1e18;
const long double EPS = 1e-9;

const int MAX_N = 55;
const int MAX = 110;
int gx, gy, N, F;
tuple<int, int, int> xyc[MAX_N];
int dp[MAX][MAX];
// [x point][y point] = min cost

int main() {
	scanf("%d%d%d%d", &gx, &gy, &N, &F);
	REP(i, N) {
		int x, y, c;
		scanf("%d%d%d", &x, &y, &c);
		xyc[i] = {x, y, c};
	}
	REP(i, MAX) fill(dp[i], dp[i] + MAX, INF);
	dp[0][0] = 0;
	REP(i, N) {
		int x, y, c;
		tie(x, y, c) = xyc[i];
		RREP(j, MAX) RREP(k, MAX) if (dp[j][k] != INF) {
			if (j + x <= gx && k + y <= gy) {
				chmin(dp[j + x][k + y], dp[j][k] + c);
			}
		}
	}
	int ans = INF;
	REP(i, gx + 1) REP(j, gy + 1) {
		chmin(ans, dp[i][j] + (gx - i) * F + (gy - j) * F);
	}
	cout << ans << endl;
}