#include <bits/stdc++.h>
#define int long long
//#define USE_FREOPEN
//#define MUL_TEST
#define FILENAME "crystal"
using namespace std;
int dp[105][105];
int dx[55],dy[55],c[55];

void solve() {
	int h,w,n,f;
	cin >> h >> w >> n >> f;
	for (int i = 1; i <= n; i++)
		cin >> dx[i] >> dy[i] >> c[i];
	memset(dp,0x3f,sizeof(dp));
	for (int x = 0; x <= h; x++) {
		for (int y = 0; y <= h; y++) {
			dp[x][y] = (x + y) * f;
		}
	}
	for (int i = 1; i <= n; i++) {
		for (int x = h; x >= 0; x--) {
			for (int y = w; y >= 0; y--) {
				if (x > 0) dp[x][y] = min(dp[x][y],dp[x - 1][y] + f);
				if (y > 0) dp[x][y] = min(dp[x][y],dp[x][y - 1] + f);
				if (x >= dx[i] && y >= dy[i]) dp[x][y] = min(dp[x][y],dp[x - dx[i]][y - dy[i]] + c[i]);
			}
		}
	}
	cout << dp[h][w] << '\n';
}

signed main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr); cout.tie(nullptr);

	#ifdef USE_FREOPEN
		freopen(FILENAME ".in","r",stdin);
		freopen(FILENAME ".out","w",stdout);
	#endif
	int _ = 1;
	#ifdef MUL_TEST
		cin >> _;
	#endif
	while (_--)
		solve();
	_^=_;
	return 0^_^0;
}