#include<bits/stdc++.h>
using namespace std;
using ll = long long;

#define FOR(i,a,b) for(ll i=(a);i<(b);++i)
#define ALL(v) (v).begin(), (v).end()
#define p(s) cout<<(s)<<endl
#define p2(s, t) cout << (s) << " " << (t) << endl
#define br() p("")
#define pn(s) cout << (#s) << " " << (s) << endl

const ll mod = 1e9 + 7;
const ll inf = 1e18;

ll M[101][101];

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

    // input
    ll Gx, Gy, N, F;
    cin >> Gx >> Gy >> N >> F;

    FOR(i, 0, 101){
        FOR(j, 0, 101){
            M[i][j] = inf;
        }
    }

    // 初期コスト
    FOR(i, 0, 101){
        FOR(j, 0, 101){
            M[i][j] = (i+j)*F;
        }
    }

    FOR(i, 0, N){
        ll x, y, c;
        cin >> x >> y >> c;
        
        FOR(i, 0, 101){
            FOR(j, 0, 101){
                ll ny = i + y;
                ll nx = j + x;
                if(ny<101 && nx<101){
                    M[ny][nx] = min(M[ny][nx], M[i][j]+c);
                }
            }
        }
    }
    
    p(M[Gy][Gx]);
    
    return 0;
}