#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 10000000

struct ST {
  int x, y, c;
};

int main(){
  int Gx, Gy, N, F;
  cin >> Gx >> Gy >> N >> F;

  vector<ST> v;
  rep(i,N){
    int x, y, c;
    cin >> x >> y >> c;
    v.push_back((ST){x,y,c});
  }

  vector<vector<int>> cost(Gy+1, vector<int>(Gx+1,INF));
  cost[0][0] = 0;
  rep(i,N){
    vector<vector<int>> new_cost = cost;
    
    rep(y,cost.size()){
      rep(x,cost[y].size()){
        if(cost[y][x] != INF){
          if(x+v[i].x<cost[y].size() && y+v[i].y<cost.size()){
            new_cost[y+v[i].y][x+v[i].x] = min(new_cost[y+v[i].y][x+v[i].x],
                                           cost[y][x] + v[i].c);
          }
        }
      }
    }

    queue<ST> que;
    que.push((ST){0,0,0});
    while(!que.empty()){
      ST st = que.front(); que.pop();
      if(st.y+1<cost.size()){
        new_cost[st.y+1][st.x] = min(new_cost[st.y+1][st.x], new_cost[st.y][st.x]+F);
        que.push((ST){st.x,st.y+1,0});
      }
      if(st.x+1<cost[st.y].size()){
        new_cost[st.y][st.x+1] = min(new_cost[st.y][st.x+1], new_cost[st.y][st.x]+F);
        que.push((ST){st.x+1,st.y,0});
      }
    }
    
    cost = new_cost;
  }

  cout << cost[Gy][Gx] << endl;
  
  return 0;
}