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

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

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)

print dp[gy][gx]