#include <iostream>
#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];

int main(){
    int gx,gy,N,F;
    cin >> gx >> gy >> N >> F;
    int x,y,c;

    for(int j = 0; j < gy+1; j++){
        for(int k = 0; k < gx+1; k++){
            dp[j][k] = F*(k+j);//初期化
            //cout << dp[j][k] << " ";
        }
       // cout << endl;
    }
 
    for(int t = 0; t < N; t++){
        cin >> x >> y >> c;
        for(int i = 0; i < gy+1; i++){
            for(int j = 0; j < gx+1; j++){
                if(i - y >= 0 && j - x >= 0){
                    dp[i][j] = min(dp[i][j],dp[i-y][j-x]+c);
                }
            }
        }
    }
/*
    for(int j = 0; j < gy+1; j++){
        for(int k = 0; k < gx+1; k++){
            cout << dp[j][k] << " ";
        }
        cout << endl;
    }
*/
    cout << dp[gy][gx] << endl;
    return 0;
}