#include <bits/stdc++.h>
#define rep(i,n) for(int i=0;i<(int)(n);i++)
using namespace std;
using ll = long long ;
using P = pair<int,int> ;
using pll = pair<long long,long long>;
constexpr int INF = 1e9;
constexpr long long LINF = 1e17;
constexpr int MOD = 1000000007;
constexpr double PI = 3.14159265358979323846;

int dp[52][105][105];

int main(){
    int w,h,n,f;
    cin >> w >> h >> n >> f;
    vector<int> x(n),y(n),c(n);
    rep(i,n){ cin >> x[i] >> y[i] >> c[i];}
    rep(i,n+1)rep(j,w+1)rep(k,h+1) dp[i][j][k] = INF;
    dp[0][0][0] = 0;
    for(int i=1;i<=n;i++){
        int xx = x[i-1];
        int yy = y[i-1];
        int cc = c[i-1];
        rep(j,w+1)rep(k,h+1){
            if(j-xx>=0 && k-yy>=0) dp[i][j][k] = min(dp[i-1][j-xx][k-yy] + cc,dp[i-1][j][k]);
            else dp[i][j][k] = dp[i-1][j][k];
        }
    }
    /*
    rep(i,n+1){
        rep(j,w+1){
            rep(k,h+1) cout << (dp[i][j][k]==INF?-1:dp[i][j][k]) << " ";
            cout << endl;
        }
        cout << endl;
    }
    */
    int ans = INF;
    rep(i,w+1)rep(j,h+1){
        ans = min(ans,dp[n][i][j] + f*(w-i+h-j));
    }
    cout << ans << endl;
    return 0;
}