#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<ctime>
#include<cctype>
#include<climits>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<memory>
#include<functional>
 
using namespace std;
 
#define ALL(g) (g).begin(),(g).end()
#define REP(i, x, n) for(int i = x; i < n; i++)
#define rep(i,n) REP(i,0,n)
#define F(i,j,k) fill(i[0],i[0]+j*j,k)
#define P(p) cout<<(p)<<endl;
#define EXIST(s,e) ((s).find(e)!=(s).end())
#define INF 1<<25
#define pb push_back
 
typedef vector<int> vi;
typedef vector<long long> vl;
typedef vector<double> vd;
typedef pair<int,int> pii;
typedef pair<long,long> pll;
typedef long long ll;
int dp[101][101];

int main(){
	int Gx,Gy,N,F;
	cin>>Gx>>Gy>>N>>F;
	int x[N+1],y[N+1],c[N+1];
	for(int i=0;i<N;i++){
		cin>>x[i]>>y[i]>>c[i];
	}
	for(int i=0;i<Gx+1;i++){
		for(int j=0;j<Gy+1;j++){
			dp[i][j]=(i+j)*F;
		}
	}
	//cout<<"debug"<<endl;
	for(int i=0;i<N;i++){
		for(int j=Gx;j>=0;j--){
			for(int k=Gy;k>=0;k--){
				if(j>=x[i]&&k>=y[i]){
					dp[j][k]=min(dp[j][k],dp[j-x[i]][k-y[i]]+c[i]);//使わない、使う
				}
			}
		}
	}
	cout<<dp[Gx][Gy]<<endl;

	return 0;
}