#include<bits/stdc++.h>
#define rep(i,n,m) for(int i = (n); i <(m); i++)
#define rrep(i,n,m) for(int i = (n) - 1; i >=(m); i--)
using namespace std;
using ll = long long;
struct crystal{int x, y, c;};

int main()
{
    int gx, gy, n, f;
    cin >> gx >> gy >> n >> f;

    vector<crystal> cry;
    rep(i, 0, n)
    {
        crystal c;
        cin >> c.x >> c.y >> c.c;
        
        cry.push_back(c);
    }

    int dp[n+1][2*gx][2*gy];
    rep(k, 0, n+1) rep(i, 0, 3*gx) rep(j, 0, 3*gy) 
        dp[k][i][j] = (i + j) * f;
    
    rep(k, 0, n)
    {
        crystal c = cry[k];
        rep(i, 0, gx + 1)
            rep(j, 0, gy + 1)
            {
                dp[k+1][i][j] = min(
                    dp[k+1][i][j],
                    dp[k][i][j]
                );
                dp[k+1][i+c.x][j+c.y] = min(
                    dp[k][i+c.x][j+c.y],
                    dp[k][i][j] + c.c
                );
            }
    }

    cout << dp[n][gx][gy] << endl;
    return 0;
}