#include<bits/stdc++.h>
using namespace std;
#ifdef LOCAL_DEBUG
  #include "LOCAL_DEBUG.hpp"
#endif
#define int long long
const int INF = 1LL << 60;

signed main(){

  int Gx, Gy, N, F; cin >> Gx >> Gy >> N >> F;
  if(N == 0){
    cout << F * (Gx + Gy) << endl;
    return 0;
  }
  static int dp[111][111][51];
  fill(dp[0][0], dp[101][101] + 50, INF);
  dp[0][0][0] = 0;
  for(int i = 0; i < N; i++){
    int x, y, c; cin >> x >> y >> c;
    for(int j = 0; j <= Gx; j++){
      for(int k = 0; k <= Gy; k++){
        dp[j][k][i+1] = min(dp[j][k][i+1], dp[j][k][i]);
        if(j + x <= Gx && k + y <= Gy){
          dp[j + x][k + y][i+1] = min(dp[j + x][k + y][i+1], dp[j][k][i] + c);
        }
      }
    }
    for(int j = 0; j <= Gx; j++){
      for(int k = 0; k <= Gy; k++){
        if(j + 1 <= Gx){
          dp[j + 1][k][i+1] = min(dp[j + 1][k][i+1], dp[j][k][i+1] + F);
        }
        if(k + 1 <= Gy){
          dp[j][k + 1][i+1] = min(dp[j][k + 1][i+1], dp[j][k][i+1] + F);
        }
      }
    }
  }
  cout << dp[Gx][Gy][N] << endl;

  return 0;
}