#include <bits/stdc++.h>
#define FOR(i,bg,ed) for(ll i=(bg);i<(ed);i++)
#define REP(i,n) FOR(i,0,n)
#define MOD 1000000007
#define int long long
using namespace std;
typedef long long ll;
const int INF = 1e9;

int dp[101][101];

signed main()
{
    int W, H, N, F, x, y, c;
    
    cin >> W >> H >> N >> F;
    REP(i,H+1) REP(j,W+1) dp[i][j] = (i + j) * F;
    REP(t,N) {
        cin >> x >> y >> c;
        for (int i=H; i>=0; i--) {
            for (int j=W; j>=0; j--) {
                if (i >= y && j >= x) dp[i][j] = min(dp[i][j], dp[i-y][j-x] + c);
            }
        }
    }
    
    cout << dp[H][W] << endl;
}