Gx,Gy,N,F = map(int,input().split())
L = []
P = [[0,0,0]]
for n in range(N):
	x,y,c = list(map(int,input().split()))
	if c / (x + y) > F:
		pass
	else:
		pi = len(P)
		for i,p in enumerate(P):
			if x + p[0] <= Gx and y + p[1] <= Gy and i < pi:
				x2 = p[0] + x
				y2 = p[1] + y
				c2 = p[2] + c
				if [x2, y2, c2] not in P:
					P.append([x2,y2,c2])
m = float("inf")
for p in P:
	x = Gx - p[0]
	y = Gy - p[1]
	c = (x + y) * F + p[2]
	if c < m:
		m = c
print(m)