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

typedef long long   signed int LL;
typedef long long unsigned int LU;

#define incID(i, l, r) for(int i = (l)    ; i <  (r); i++)
#define incII(i, l, r) for(int i = (l)    ; i <= (r); i++)
#define decID(i, l, r) for(int i = (r) - 1; i >= (l); i--)
#define decII(i, l, r) for(int i = (r)    ; i >= (l); i--)
#define  inc(i, n) incID(i, 0, n)
#define inc1(i, n) incII(i, 1, n)
#define  dec(i, n) decID(i, 0, n)
#define dec1(i, n) decII(i, 1, n)

#define inII(v, l, r) ((l) <= (v) && (v) <= (r))
#define inID(v, l, r) ((l) <= (v) && (v) <  (r))

#define PB push_back
#define EB emplace_back
#define MP make_pair
#define FI first
#define SE second
#define UB upper_bound
#define LB lower_bound
#define PQ priority_queue

#define  ALL(v)  v.begin(),  v.end()
#define RALL(v) v.rbegin(), v.rend()
#define  FOR(it, v) for(auto it =  v.begin(); it !=  v.end(); ++it)
#define RFOR(it, v) for(auto it = v.rbegin(); it != v.rend(); ++it)

template<typename T> bool   setmin(T & a, T b) { if(b <  a) { a = b; return true; } else { return false; } }
template<typename T> bool   setmax(T & a, T b) { if(b >  a) { a = b; return true; } else { return false; } }
template<typename T> bool setmineq(T & a, T b) { if(b <= a) { a = b; return true; } else { return false; } }
template<typename T> bool setmaxeq(T & a, T b) { if(b >= a) { a = b; return true; } else { return false; } }
template<typename T> T gcd(T a, T b) { return (b == 0 ? a : gcd(b, a % b)); }
template<typename T> T lcm(T a, T b) { return a / gcd(a, b) * b; }

// ---- ----

int gx, gy, n, f, x[50], y[50], c[50];
int dp[101][101][51];
const int INF = 50000;

int main() {
	cin >> gx >> gy >> n >> f;
	inc(i, n) { cin >> x[i] >> y[i] >> c[i]; }
	
	inc(i, n + 1) {
		inc(xx, gx + 1) {
		inc(yy, gy + 1) {
			dp[xx][yy][i] = INF;
		}
		}
	}
	inc(i, n + 1) { dp[0][0][i] = 0; }
	
	inc(i, n) {
		inc(xx, gx + 1) {
		inc(yy, gy + 1) {
			if((x[i] + y[i]) * f <= c[i]) { continue; }
			int xxx = xx + x[i];
			int yyy = yy + y[i];
			if(xxx <= gx && yyy <= gy) {
				incII(j, i + 1, n) { setmin(dp[xxx][yyy][j], dp[xx][yy][i] + c[i]); }
			}
		}
		}
	}
	
	int ans = INF;
	inc(xx, gx + 1) {
	inc(yy, gy + 1) {
		setmin(ans, dp[xx][yy][n] + (gx - xx + gy - yy) * f);
	}
	}
	
	cout << ans << endl;
	
	return 0;
}