#include <iostream>
#include <vector>
#include <algorithm>
#include <cstdio>
using namespace std;

#define INF 1930000000
const int MAX_N = 50;
const int MAX_X = 100;
const int MAX_Y = 100;
int dp[MAX_X+1][MAX_Y+1];//50 * 10000 = 500,000
bool check[MAX_X+1][MAX_Y+1];

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 j = 0; j < gx+1; j++){
        for(int k = 0; k < gy+1; k++){
            dp[j][k] = INF;//初期化   
        }
    }
 
    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});
        }
    }
    if(cry.size() == 0){
        cout << (gx+gy)*F << endl;
        return 0;
    }
    sort(cry.begin(),cry.end(),comp);
    
    dp[0][0] = 0;
    dp[cry[0].x][cry[0].y] = cry[0].c;
    dp[gx][gy] = cry[0].c + (gx- cry[0].x + gy - cry[0].y)* F;

    for(int i = 0; i < cry.size();i++){
        for(int j = 0; j < gx+1; j++){
            for(int k = 0; k < gy+1; k++){
                check[j][k] = false;//初期化
            }
        }

        for(int j = 0; j <= gx; j++){
            for(int k = 0; k <= gy; k++){
                if(j-cry[i].x >= 0 && k-cry[i].y >= 0){
                    if(check[j-cry[i].x][k-cry[i].y] == false){
                        dp[j][k] = min(dp[j][k], dp[j - cry[i].x][k - cry[i].y]+cry[i].c);
                        check[j][k] = true;
                    }
                }
                
                dp[gx][gy] = min(dp[gx][gy] ,dp[j][k]+(gx-j + gy-k)*F);
            }
        }
    }

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