#include<map>
#include<set>
#include<list>
#include<cmath>
#include<queue>
#include<stack>
#include<cstdio>
#include<string>
#include<vector>
#include<complex>
#include<cstdlib>
#include<cstring>
#include<numeric>
#include<sstream>
#include<iostream>
#include<algorithm>
#include<functional>
 
#define mp       make_pair
#define pb       push_back
#define all(x)   (x).begin(),(x).end()
#define YES() printf("YES\n")
#define NO() printf("NO\n")
 
using namespace std;
 
#define int long long
//typedef    long long          ll;
typedef    unsigned long long ull;
typedef    vector<bool>       vb;
typedef    vector<int>        vi;
typedef    vector<vb>         vvb;
typedef    vector<vi>         vvi;
//typedef    pair<int,int>      P;
 
const int INF=1e+13;
const double EPS=1e-9;
 
const int dx[]={1,0,-1,0},dy[]={0,-1,0,1};

signed main(){
	int gx,gy,n,f;
	int dp[51][101][101];
	cin >> gx >> gy >> n >> f;
	for(int i = 0;i <= n;i++){
		for(int j = 0;j <= gx;j++){
			for(int k = 0;k <= gy;k++) dp[i][j][k] = INF;
		}
	}
	dp[0][0][0] = 0;
	for(int i = 0;i < n;i++){
		int x,y,c;
		cin >> x >> y >> c;
		for(int j = 0;j <= gx;j++){
			for(int k = 0;k <= gy;k++){
				if(j + x <= gx && k + y <= gy){
					dp[i + 1][j + x][k + y] = min(dp[i + 1][j + x][k + y],dp[i][j][k] + c);
				}
				dp[i + 1][j][k] = min(dp[i + 1][j][k],dp[i][j][k]);
			}
		}
	}
	int mi = INF;
	for(int i = 0;i <= gx;i++){
		for(int j = 0;j <= gy;j++){
			mi = min(mi,dp[n][i][j] + (gx + gy - i - j) * f);
		}
	}
	cout << mi << endl;
	return 0;
}