#include <bits/stdc++.h>
using namespace std;

#define rep(i,j,n) for(int i=j;i<n;++i)
#define all(i) i.begin(),i.end()
#define rall(i) i.rbegin(), i.rend()
#define INF 1e9
#define LINF 1e18
const int mod = 1e9 + 7;

typedef long long i64;
typedef pair<int, int> pi;

template <class T> using vt = vector<T>;
template <class T> using vvt = vector<vector<T>>;

i64 gcd(i64 n, i64 m) {return (m == 0? n : gcd(m, n % m));}
i64 lcd(i64 n, i64 m) {return (n / gcd(n, m) * m);}
int dx[] = {1, 0, -1, 0};
int dy[] = {0, 1, 0, -1};

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

  int gx, gy, n, f;
  cin >> gx >> gy >> n >> f;
  vt<int> x(n), y(n), c(n);
  rep(i, 0, n) cin >> x[i] >> y[i] >> c[i];

  vvt<int> dp(110, vt<int>(110, INF));
  dp[0][0] = 0;
  rep(i, 0, gx + 1) {
    rep(j, 0, gy + 1) {
      dp[i + 1][j] = min(dp[i + 1][j], dp[i][j] + f);
      dp[i][j + 1] = min(dp[i][j + 1], dp[i][j] + f);
    }
  }

  rep(k, 0, n) {
    auto vec = dp;
    rep(i, 0, gx + 1) {
      rep(j, 0, gy + 1) {
        vec[i][j] = dp[i][j];
        if(i >= x[k] && j >= y[k]) vec[i][j] = min(vec[i][j], dp[i - x[k]][j - y[k]] + c[k]);
      }
    }
    swap(vec, dp);
  }
  cout << dp[gx][gy] << endl;
}