#if 1
#include <iostream>
#include <fstream>
#include <string>
#include <vector>
#include <map>
#include <set>
#include <unordered_map>
#include <unordered_set>
#include <queue>
#include <stack>
#include <array>
#include <deque>
#include <algorithm>
#include <utility>
#include <cstdint>
#include <functional>
#include <iomanip>
#include <numeric>

#define in std::cin
#define out std::cout

template<typename T>
void fill_all(T& arr, const T& v) {
	arr = v;
}
template<typename T, typename ARR>
void fill_all(ARR& arr, const T& v) {
	for (auto& i : arr) { fill_all(i, v); }
}

int Gx, Gy;
int32_t N,F;
int X[100];
int Y[100];
int C[100];
constexpr int INF = 1000000000;
int32_t DP[101][101][51];
int32_t func(int x, int y, int i)
{
	if (x > Gx || y > Gy) { return INF; }
	if (i == N) {
		return F*(Gx - x + Gy - y);
	}
	if (DP[x][y][i] != -1) {
		return DP[x][y][i];
	}
	return DP[x][y][i] =
		std::min(
			func(x+X[i],y + Y[i],i+1) + C[i],
			func(x, y, i + 1)
		)
		;
}

int main()
{
	using std::endl;
	in.sync_with_stdio(false);
	out.sync_with_stdio(false);
	fill_all(DP, -1);
	in >> Gx>>Gy>>N>>F;
	for (size_t i = 0; i < N; i++)
	{
		in >> X[i] >> Y[i] >> C[i];
	}

	out << func(0, 0, 0) << endl;

	return 0;
}
#endif