#include <bits/stdc++.h>
using namespace std;
#define REP(i,a,n) for(int i=(a); i<(int)(n); i++)
#define rep(i,n) REP(i,0,n)
#define FOR(it,c) for(__typeof((c).begin()) it=(c).begin(); it!=(c).end(); ++it)
#define ALLOF(c) (c).begin(), (c).end()
typedef long long ll;
typedef unsigned long long ull;

#define INF 100000000

int main(){
  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];
  }

  vector<vector<int>> dp(gy+1,vector<int>(gx+1,INF));
  rep(yy,gy+1){
    rep(xx,gx+1){
      dp[yy][xx] = F * (yy+xx);
    }
  }
  
  rep(i,N){
    for(int yy=gy; yy>=0; yy--){
      for(int xx=gx; xx>=0; xx--){
        if(yy-y[i]>=0 && xx-x[i]>=0){
          dp[yy][xx] = min(dp[yy][xx],
                           dp[yy-y[i]][xx-x[i]] + c[i]);
        }
      }
    }
  }
  
  cout << dp[gy][gx] << endl;
  
  return 0;
}