#include <algorithm>
#include <iostream>
#include <vector>
using namespace std;

int main() {
    int gx, gy, n, f;
    cin >> gx >> gy >> n >> f;
    vector<vector<int>> dp(gx + 1, vector<int>(gy + 1));
    for (int i = 0; i <= gx; i++) for (int j = 0; j <= gy; j++) {
        dp[i][j] = (i + j) * f;
    }
    while (n--) {
        int a, b, c; cin >> a >> b >> c;
        for (int i = gx; i >= a; i--) for (int j = gy; j >= b; j--) {
            dp[i][j] = min(dp[i][j], dp[i - a][j - b] + c);
        }
    }
    cout << dp[gx][gy] << endl;
    return 0;
}