#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 Gx, Gy, N, F;
int x[300], y[300], c[300];
int dp[300][300];

signed main()
{
    cin >> Gx >> Gy >> N >> F;
    int idx;
    for (idx=0; idx<N; idx++) cin >> x[idx] >> y[idx] >> c[idx];
    REP(i,Gx) {
        x[idx] = 1; y[idx] = 0; c[idx] = F;
        idx++;
    }
    REP(i,Gy) {
        x[idx] = 0; y[idx] = 1; c[idx] = F;
        idx++;
    }

    REP(x,300) REP(y,300) dp[x][y] = INF;

    dp[0][0] = 0;
    for (int tx=0; tx<=Gx; tx++) {
        for (int ty=0; ty<=Gy; ty++) {
            REP(i,idx) {
                dp[tx+x[i]][ty+y[i]] = min(dp[tx+x[i]][ty+y[i]], dp[tx][ty] + c[i]);
            }
        }
    }

    cout << dp[Gx][Gy] << endl;
}