import sequtils
template times*(n:int,body) = (for _ in 0..<n: body)
template `min=`*(x,y) = x = min(x,y)

proc getchar_unlocked():char {. importc:"getchar_unlocked",header: "<stdio.h>" .}
proc scan(): int =
  while true:
    let k = getchar_unlocked()
    if k < '0': return
    result = 10 * result + k.ord - '0'.ord
const INF = 1e10.int
let gx = scan()
let gy = scan()
let n = scan()
let f = scan()
var dp : array[101,array[101,int]]
for x in 0..gx:
  for y in 0..gy:
    dp[x][y] = f * (x + y)
n.times:
  let cx = scan()
  let cy = scan()
  let cost = scan()
  for x in (gx-cx).countdown(0):
    for y in (gy-cy).countdown(0):
      dp[x+cx][y+cy] .min= dp[x][y] + cost
echo dp[gx][gy]