#include <iostream>
#include <vector>
#include <algorithm>
#include <map>
#include <string>
#include <queue>
#include <stack>
#include <math.h>
#include <set>
#include <cstdio>
#define ALL(obj) (obj).begin(),(obj).end()
#define RALL(obj) (obj).rbegin(),(obj).rend()
#define P pair<int, int>

#define MOD 1000000007
#define INF 1012345678
#define NINF (-2147483647-1)
#define LLINF 9223372036854775807
using ll = long long;
using namespace std;

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    int gx, gy, N, F;
    cin >> gx >> gy >> N >> F;
    vector<vector<int>> dp(gx + 1, vector<int>(gy + 1,INF));
    dp[0][0] = 0;
    for (int i = 0; i < N; i++)
    {
        int x, y, cost;
        cin >> x >> y >> cost;
        for (int j = 0; j <= gx; j++)
        {
            for (int k = 0; k <= gy; k++)
            {
                if (j - x >= 0 && k - y >= 0) {
                    dp[j][k] = min(dp[j][k], dp[j - x][k - y] + cost);
                }
            }
        }
    }
    int ans = INF;
    for (int i = 0; i <= gx; i++)
    {
        for (int j = 0; j <= gy; j++)
        {
            ans = min(ans, dp[i][j] + (gx - i + gy - j) * F);
        }
    }
    cout << ans << endl;
    getchar(); getchar();
}