#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+9;
const double EPS=1e-9;
 
const int dx[]={1,0,-1,0},dy[]={0,-1,0,1};

struct edge{ int tox,toy,cost; };
typedef pair<int,int> POS;
typedef pair<int,POS> P;

signed main(){
	int gx,gy,n,f;
	vector<edge> G[101][101];
	int d[101][101];
	cin >> gx >> gy >> n >> f;
	for(int i = 0;i < n;i++){
		int x,y,c;
		cin >> x >> y >> c;
		for(int j = 0;j <= gx - x;j++){
			for(int k = 0;k <= gy - y;k++) G[j][k].push_back({j + x,k + y,c});
		}
	}
	for(int i = 0;i <= gx;i++){
		for(int j = 0;j <= gy;j++) {
			if(i != gx) G[i][j].push_back({i + 1,j,f});
			if(j != gy) G[i][j].push_back({i,j + 1,f});
		}
	}
	for(int i = 0;i <= gx;i++){
		for(int j = 0;j <= gy;j++) {
			d[i][j] = INF;
		}
	}
	d[0][0] = 0;
	priority_queue<P,vector<P>,greater<P> > que;
	que.push(mp(0,mp(0,0)));
	while(!que.empty()){
		P p = que.top();que.pop();
		int cost = p.first,x = p.second.first,y = p.second.second;
		if(d[x][y] < cost) continue;
		for(int i = 0;i < G[x][y].size();i++){
			edge e = G[x][y][i];
			if(d[e.tox][e.toy] > d[x][y] + e.cost){
				d[e.tox][e.toy] = d[x][y] + e.cost;
				que.push(mp(d[e.tox][e.toy],mp(e.tox,e.toy)));
			}
		}
	}
	cout << d[gx][gy] << endl;
	return 0;
}