R=xrange;I=lambda:map(int,raw_input().split())
Gx,Gy,N,F=I()
assert 0 <= Gx <= 100
assert 0 <= Gy <= 100
assert 0 <= N <= 50
assert 1 <= F <= 200
dp=[[F*(i+j) for j in R(Gx+1)]for i in R(Gy+1)]
for t in R(N):
	x,y,c = I()
	assert 0 <= x <= Gx
	assert 0 <= y <= Gy
	assert (x,y) != (0,0)
	assert 1 <= c <= 200
	for i in R(Gy,y-1,-1):
		for j in R(Gx,x-1,-1):
			dp[i][j]=min(dp[i][j],dp[i-y][j-x]+c)
print dp[Gy][Gx]