#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

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