#include <cmath>
#include <vector>
#include <list>
#include <map>
#include <set>
#include <functional>
#include <queue>
#include <iostream>
#include <string.h>
#include <iomanip>
#include <algorithm>
#include <functional>
#include <cstdint>
#include <climits>
#include <unordered_set>
#include <sstream>
#include <stack>

using namespace std;

typedef long long int ll;
typedef pair<int,int> pii;
typedef tuple<ll,ll,ll> t3;

using namespace std;

#define MAX_N 110

int dp[MAX_N][MAX_N][MAX_N];

int main(){
    int gx,gy,n,f;
    cin >> gx >> gy >> n >> f;
    for(int y = 0;y <= gy;y++)
    {
        for(int x = 0;x <= gx;x++)
        {
            dp[0][y][x] = (x + y) * f;
        }
    }
    for(int i = 0;i < n;i++)
    {
        int sx,sy,sc;
        cin >> sx >> sy >> sc;
        for(int y = 0;y <= gy;y++)
        {
            for(int x = 0;x <= gx;x++)
            {
                dp[i+1][y][x] = dp[i][y][x];
            }
        }
        for(int y = 0;y <= gy;y++)
        {
            ll ny = sy + y;
            if(ny > gy)
            {
                continue;
            }
            for(int x = 0;x <= gx;x++)
            {
                ll nx = sx + x;
                if(nx > gx)
                {
                    continue;
                }
                dp[i+1][ny][nx] = min(dp[i+1][ny][nx], dp[i][y][x] + sc);
            }
        }
        for(int y = 0;y <= gy;y++)
        {
            for(int x = 0;x <= gx;x++)
            {
                if(x > 0)
                {
                    dp[i+1][y][x] = min(dp[i+1][y][x], dp[i+1][y][x-1] + f);
                }
                if(y > 0)
                {
                    dp[i+1][y][x] = min(dp[i+1][y][x], dp[i+1][y-1][x] + f);
                }
            }
        }
    }
    cout << dp[n][gy][gx] << endl;
    return 0;
}