#include <algorithm>
#include <cstdio>
#include <iostream>
#include <map>
#include <cmath>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>
#include <stdlib.h>
#include <stdio.h>
#include <bitset>
using namespace std;
#define FOR(I,A,B) for(int I = (A); I < (B); ++I)

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