CommonFun.calcBuff_7840
function CommonFun.calcBuff_7840(srcUser, targetUser, a, b, c, d, lv)
  if srcUser == nil or targetUser == nil then
    return 0
  end
  local layer = srcUser:GetBuffLayer(187560_THE_ATTACK_DEALS_HP_DAMAGE_TO_ENEMY_:MAX_STACK_3)
  local Maxhp = targetUser:GetProperty("MaxHp")
  local A = layer * Maxhp * 0.001
  return -A
end