#include <bits/stdc++.h>

using namespace std;

#define REP(i,n) for(int i=0; i<(int)(n); i++)
#define FOR(i,b,e) for (int i=(int)(b); i<(int)(e); i++)
#define ALL(x) (x).begin(), (x).end()

const double PI = acos(-1);
const int INF = 1e9;

int dp[101][101];

int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);

  int gx, gy, n, f;
  cin >> gx >> gy >> n >> f;

  vector<int> x(n), y(n), c(n);
  REP (i, n)
    cin >> x[i] >> y[i] >> c[i];

  REP (i, 101) REP (j, 101) dp[i][j] = INF;
  dp[0][0] = 0;
  
  REP (k, n) {
    for (int i = gy; i >= 0; i--) {
      for (int j = gx; j >= 0; j--) {
        if (i-y[k] >= 0 && j-x[k] >= 0)
          dp[i][j] = min(dp[i][j], dp[i-y[k]][j-x[k]] + c[k]);
      }
    }
  }

  int ret = INF;
  for (int i = 0; i <= gy; i++) {
    for (int j = 0; j <= gx; j++) {
      int dist = (gy - i) + (gx - j);
      ret = min(ret, dp[i][j] + f * dist);
    }
  }
  cout << ret << endl;
  
  return 0;
}