#!/usr/bin/env python3
# %%
import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines


# %%
import numpy as np

# %%
Gx, Gy, N, F = map(int, readline().split())
m = map(int, read().split())
XYC = tuple(zip(m, m, m))


# %%
INF = 10 ** 16
dp = np.full((Gx + 1, Gy + 1), INF, np.int64)
dp[0, 0] = 0


# %%
for x, y, c in XYC:
    np.minimum(
        dp[x: Gx + 1, y: Gy + 1], dp[0: Gx + 1 - x, 0: Gy + 1 - y] + c,
        out=dp[x:Gx + 1, y:Gy + 1])

# %%
dp += F * (np.arange(Gx + 1)[::-1][:, None] + np.arange(Gy + 1)[::-1][None, :])
answer = dp.min()
print(answer)