#include <bits/stdc++.h>
using namespace std;
 
#define rep(i,a,b) for(int i=a;i<b;i++)
#define int long long
const int inf = 100100100100100;
const int mod = 1000000007;

signed main(){
    std::ios::sync_with_stdio(false);
    std::cin.tie(0);

    int x,y, n, f;
    cin >> x >> y >> n >> f;

    int dp[y+1][x+1];
    dp[0][0] = 0;
    rep(i,1,y+1){
        dp[i][0] = dp[i-1][0] + f;
    }
    rep(i,0,y+1){
        rep(j,1,x+1){
            dp[i][j] = dp[i][j-1] + f;
        }
    }

    int crystals[n][3];


    rep(i,0,n){
        rep(j,0,3){
            cin >> crystals[i][j];
        }
    }


    rep(k,0,n){
        for(int i = y; i > -1; i--){
            for(int j = x; j > -1; j--){
                int dx = j-crystals[k][0];
                int dy = i-crystals[k][1];
                if(-1 < dx && -1 < dy){
                    dp[i][j] = min(dp[i][j], dp[dy][dx] + crystals[k][2]);
                }
          } 
        }
    }

    cout << dp[y][x] << endl;

}