#pragma GCC target("avx2")
#pragma GCC optimize("03")
#pragma GCC optimize("unroll-loops")
#include <bits/stdc++.h>
using namespace std; typedef long double ld; typedef long long ll;
typedef unsigned long long ull;
#define endl "\n"
#define FOR(i,a,b) for(int i=(a);i<=(b);i++)
#define rep(i,n) for(int i=0;i<(n);i++)
#define PII pair<int, int>
#define PLL pair<ll, ll>
#define ALL(x) (x).begin(), (x).end()
constexpr int INF=1<<30; constexpr ll LINF=1LL<<60; constexpr ll mod=1e9+7; constexpr int NIL = -1;
template <class T> vector<T> vec(int len, T elem) { return vector<T>(len, elem); }
template<class T>inline bool chmax(T &a, const T &b) { if (a<b) { a = b; return 1; } return 0; }
template<class T>inline bool chmin(T &a, const T &b) { if (b<a) { a = b; return 1; } return 0; }
template<class T>inline int popcount(T a) {return __builtin_popcount(a);}
template<class T>inline T emod(T a, T p) { return (a%p + p) % p;}
//-------------------
int main() {
    cin.tie(0); ios::sync_with_stdio(false); cout << fixed << setprecision(15);
    int Gx, Gy, n, F; cin >> Gx >> Gy >> n >> F;
    auto dp = vec(103, vec(103, INF));
    rep(i, Gx+1) rep(j,Gy+1) dp[j][i] = (i+j) * F;
    FOR(i,1,n) {
        int x1, y1, c; cin >> x1 >> y1 >> c;
        for(int y=Gy; y>=0; y--) {
            for(int x=Gx; x>=0; x--) {
                if(x-x1 >= 0 and y-y1>=0) chmin(dp[y][x], dp[y-y1][x-x1]+c);
            }
        }
    }
    cout << dp[Gy][Gx] << endl;
    return 0;
}