gx,gy,n,cc=gets.split.map &:to_i
h={}
hh={}
n.times do
  g=gets.split.map &:to_i
  h.each do |e,v|
    if (gg0=e[0]+g[0])<=gx && (gg1=e[1]+g[1])<=gy
      gg2=[gg0,gg1]
      if hh[gg2]
        hh[gg2]=g[2]+v if hh[gg2]>g[2]+v
      else
        hh[gg2]=g[2]+v
      end
    end
  end
  hh[[g[0],g[1]]]=g[2]
  h=hh.dup
end
x=gx+gy
c=x*cc
h.each do |e,v|
  g=v+(x-e[0]-e[1])*cc
  c=g if c>g
end
p c