#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const int INF=1e9;
int main(){
    int gx,gy,n,f;cin >> gx >> gy >> n >> f;
    vector<int> x(n),y(n),c(n);
    for(int i=0;i<n;i++){
        cin >> x[i] >> y[i] >> c[i];
    }
    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;
        }
    }
    for(int i=0;i<n;i++){
        for(int j=0;j<=gx;j++){
            for(int k=0;k<=gy;k++){
                if(j+x[i]<=gx&&k+y[i]<=gy){
                    dp[j+x[i]][k+y[i]]=min(dp[j+x[i]][k+y[i]],dp[j][k]+c[i]);
                }
            }
        }
    }
    cout << dp[gx][gy] << endl;
}