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

inf = float("inf")
dp = [[inf for i in range(gx+3)] for i in range(gy+3)]
dp[0][0] = 0

arr = [map(int,raw_input().split()) for i in range(n)]

for i in range(n):
	tx, ty , cost = arr[i]
	for y in range(gy+1):
		for x in range(gx+1):
			dx = x + tx; dy = y + ty

			if dx < gx + 1 and dy < gx + 1 and dp[y][x] != inf :
				dp[dy][dx] = min(dp[dy][dx], dp[y][x] + cost)

for i in range(1,gx+1):
	dp[0][i] = min(dp[0][i-1] + f, dp[0][i])

for i in range(1,gy+1):
	dp[i][0] = min(dp[i-1][0] + f, dp[i][0])

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

print dp[gy][gx]