n,A,B,w,*c=`dd`.split.map &:to_i
def d c,s
  x,*y,z=*c,B*s-A
  c[1]||(return [x,z].min)
  return x+d(y,1)if x<=z
  return z+d(y,s+1)
end
p d(c,1)+w