#include <iostream>
#include <vector>
#define repeat(i,n) for (int i = 0; (i) < int(n); ++(i))
#define repeat_reverse(i,n) for (int i = (n)-1; (i) >= 0; --(i))
using namespace std;
template <class T> inline void setmin(T & a, T const & b) { a = min(a, b); }
template <typename X, typename T> auto vectors(X x, T a) { return vector<T>(x, a); }
template <typename X, typename Y, typename Z, typename... Zs> auto vectors(X x, Y y, Z z, Zs... zs) { auto cont = vectors(y, z, zs...); return vector<decltype(cont)>(x, cont); }
constexpr int inf = 1e9+7;
int main() {
    int w, h, n, f; cin >> w >> h >> n >> f;
    vector<int> dx(n), dy(n), c(n); repeat (i,n) cin >> dx[i] >> dy[i] >> c[i];
    auto is_on_field = [&](int y, int x) { return 0 <= y and y <= h and 0 <= x and x <= w; };
    auto dp = vectors(h+1, w+1, inf);
    repeat (y,h+1) repeat (x,w+1) {
        dp[y][x] = (y + x) * f;
    }
    repeat (i,n) {
        repeat_reverse (y,h+1) repeat_reverse (x,w+1) {
            int ny = y - dy[i];
            int nx = x - dx[i];
            if (is_on_field(ny, nx)) {
                setmin(dp[y][x], dp[ny][nx] + c[i]);
            }
        }
    }
    cout << dp[h][w] << endl;
    return 0;
}