#!/usr/bin/python

Gx, Gy, N, F = list(map(int, input().split()))
crystal = []
for i in range(N):
    crystal.append(tuple(map(int, input().split())))
    
crystal = tuple(crystal)
    
dp = [[(i + j) * F for i in range(Gx + 1)] for j in range(Gy + 1)]

for i in range(N):
    cx, cy, cc = crystal[i]
    for y in range(Gy, -1, -1):
        for x in range(Gx, -1, -1):
            if y >= cy and x >= cx:
                dp[y][x] = min(dp[y][x], dp[y - cy][x - cx] + cc)

print (dp[Gy][Gx])