#define TEST_MODE true

#define _CRT_SECURE_NO_WARNINGS
#define _USE_MATH_DEFINES

#include "bits/stdc++.h"
using namespace std;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i, a, b) for (int i = (a); i < (b); ++i)
#define rrep(i, n) for (int i = (n)-1; i >= 0; --i)
#define rrep2(i, a, b) for (int i = (a)-1; i >= b; --i)
#define range(i, a, b, c) for (int i = a;             \
                               c > 0 ? i < b : i > b; \
                               i += c)
#define chmax(a, b) (a = (a) < (b) ? (b) : (a))
#define chmin(a, b) (a = (a) > (b) ? (b) : (a))
using ll = long long;
using ull = unsigned long long;
using ld = long double;
#define all(a) begin(a), end(a)
#define ifnot(a) if (not(a))
#define int long long

#ifdef LOCAL_ENV

#if TEST_MODE == true
const bool test = true;
#define dump(x) cerr << #x << " = " << (x) << endl
#else
const bool test = false;
#define dump(x) 
#endif

#else
const bool test = false;
#define dump(x) 
#endif

int dx[] = {1, 0, -1, 0};
int dy[] = {0, 1, 0, -1};
const int INF = (int)1 << 60;
const ll INFL = (ll)1 << 60;
ll mod_n = (int)1e9 + 7;
const double eps = 1e-10;
typedef long double Real;
// return -1, 0, 1
int sgn(const Real &r) { return (r > eps) - (r < -eps); }
int sgn(const Real &a, const Real &b) { return sgn(a - b); }

//.....................
const int MAX = (int)2e5 + 5;

vector<string> split(const string &str, char sep)
{
    vector<string> v;
    stringstream ss(str);
    string buffer;
    while (getline(ss, buffer, sep))
    {
        v.push_back(buffer);
    }
    return v;
}

template <class InputIterator>
int sum(InputIterator begin, InputIterator end)
{
    return accumulate(begin, end, 0ll);
}

void solve();

signed main()
{
    cout << fixed << setprecision(20);
    solve();
    while (true)
    {
        char s[MAX];
        if (scanf("%s", s) == EOF)
            break;
        int n = strlen(s);
        for (int i = n - 1; i > -1; i--)
        {
            ungetc(s[i], stdin);
        }
        solve();
    }
    return 0;
}

class Mycin {
	bool flag = true;
public:
	Mycin& operator >> (int& a) {flag = scanf("%lld", &a) != EOF; return *this;}
	Mycin& operator >> (char& a) {flag = scanf("%c", &a) != EOF; return *this;}
	Mycin& operator >> (string& s) {flag = (bool)(cin >> s); return *this;}
	operator bool() {return flag;}
} mycin;
 
class Mycout {
public:
	Mycout& operator << (const int& a) {printf("%lld", a); return *this;}
	Mycout& operator << (const char c) {printf("%c", c); return *this;}
	Mycout& operator << (const string& s) {printf("%s", s.c_str()); return *this;}
} mycout;
 
#define cin mycin
#define cout mycout
#define endl '\n'

int Gx, Gy, N, F;
int x[55];
int y[55];
int c[55];

int dp[105][105];

void solve() {
    cin >> Gx >> Gy >> N >> F;
    rep(i, N) cin >> x[i] >> y[i] >> c[i];
    rep(y, 105) rep(x, 105) dp[y][x] = INF;
    dp[0][0] = 0;
    rep(i, N) {
        rrep(cur_y, 105 - y[i]) rrep(cur_x, 105 - x[i]) {
            int next_y = cur_y + y[i];
            int next_x = cur_x + x[i];
            dp[next_y][next_x] = min(dp[next_y][next_x],
                                    dp[cur_y][cur_x] + c[i]);                
        }
    }
    int res = INF;
    rep(y, Gy + 1) rep(x, Gx + 1) {
        res = min(res, dp[y][x] + (Gy - y + Gx - x) * F);
    }
    cout << res << endl;
}