#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

struct crystal{
    int x;
    int y;
    int c;
    int safe;
};

bool comp(const crystal &a, const crystal &b){
    if(a.safe < b.safe) return true;
    return false;
}


int main(){
    int gx,gy,N,F;
    cin >> gx >> gy >> N >> F;
vector<crystal> cry;
int x,y,c,safe=0;
    for(int i = 0; i < N;i++){
        cin >> x >> y >> c;
        safe = (x+y)*F - c;
        if(safe > 0){
            cry.push_back({x,y,c,safe});
        }
    }

    sort(cry.begin(),cry.end(),comp);
    /*
    for(auto e : cry){
        cout << e.x << "," << e.y << "," << e.c << "," << e.safe << endl;
    }*/
    int tcost = 0,px=0,py=0;
    for(int i = 0; i < N; i++){
        if(px + cry[i].x <= gx && py + cry[i].y <= gy){
            px += cry[i].x;
            py += cry[i].y;
            tcost += cry[i].c;
        }
    }
    tcost += (gx-py)*F;
    tcost += (gy-py)*F;
    cout << tcost << endl;

    return 0;
}