gx, gy, n, f = map(int,raw_input().split())

inf = float("inf")
dp = [[inf for i in range(gx+1)] for i in range(gy+1)]; dp[0][0] = 0
arr = [map(int,raw_input().split()) for i in range(n)]

for i in range(gy + 1):
	for j in range(gx + 1):
		dp[i][j] = min(dp[i][j], (dp[i-1][j] + f) if i-1 > -1 else inf, (dp[i][j-1] + f) if j-1 > -1 else inf)


for x,y,cost in arr:
	for i in range(gy + 1):
		for j in range(gx + 1):
			dx = j + x; dy = i + y
			if -1 < dx < gx + 1 and -1 < dy < gy + 1 :
				dp[dy][dx] = min(dp[i][j] + cost, dp[dy][dx])

print dp[gy][gx]