from collections import defaultdict
import sys
input = sys.stdin.buffer.readline
sys.setrecursionlimit(10 ** 7)
inf = 10**9

gx, gy, n, f = map(int, input().split())
H = gx + 1
W = gy + 1

dp = [inf] * (H * W)
dp[0] = 0
for _ in range(n):
    x, y, c = map(int, input().split())
    for i in range(H)[::-1]:
        for j in range(W)[::-1]:
            nx = x + i
            ny = y + j
            if nx < H and ny < W:
                to = nx * W + ny
                dp[to] = min(dp[to], dp[i*W+j] + c)

ans = inf
for i in range(H):
    for j in range(W):
        cost = f * (gx+gy-i-j)
        ans = min(ans, dp[i*W+j]+cost)
print(ans)