#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;

typedef int _loop_int;
#define REP(i,n) for(_loop_int i=0;i<(_loop_int)(n);++i)
#define FOR(i,a,b) for(_loop_int i=(_loop_int)(a);i<(_loop_int)(b);++i)
#define FORR(i,a,b) for(_loop_int i=(_loop_int)(b)-1;i>=(_loop_int)(a);--i)

#define DEBUG(x) cout<<#x<<": "<<x<<endl
#define DEBUG_VEC(v) cout<<#v<<":";REP(i,v.size())cout<<" "<<v[i];cout<<endl
#define ALL(a) (a).begin(),(a).end()

#define CHMIN(a,b) a=min((a),(b))
#define CHMAX(a,b) a=max((a),(b))

// mod
const ll MOD = 1000000007ll;
#define FIX(a) ((a)%MOD+MOD)%MOD

// floating
typedef double Real;
const Real EPS = 1e-11;
#define EQ0(x) (abs(x)<EPS)
#define EQ(a,b) (abs(a-b)<EPS)
typedef complex<Real> P;

int w,h;
int n,f;

int dp[125][125];

int main(){
  scanf("%d%d%d%d",&w,&h,&n,&f);
  w++;h++;
  REP(i,125)REP(j,125)dp[i][j] = (i+j)*f;
  while(n--){
    int x,y,c;
    scanf("%d%d%d",&x,&y,&c);
    FORR(i,0,125)FORR(j,0,125){
      if(i>=x && j>=y)CHMIN(dp[i][j], dp[i-x][j-y]+c);
    }
  }
  printf("%d\n",dp[w-1][h-1]);
  return 0;
}