local pi = math.pi
local mab = math.abs
local mfl = math.floor

local function comp(a, b)
  return a < b
end

local function lower_bound(ary, x)
  local num = #ary
  if num == 0 then return 1 end
  if not comp(ary[1], x) then return 1 end
  if comp(ary[num], x) then return num + 1 end
  local min, max = 1, num
  while 1 < max - min do
    local mid = mfl((min + max) / 2)
    if comp(ary[mid], x) then
      min = mid
    else
      max = mid
    end
  end
  return max
end

local function printformat(num)
  print(string.format("%.13f", num))
end
local sx, sy = io.read("*n", "*n")
local tx, ty = io.read("*n", "*n")
local m = io.read("*n")
if sx == tx then
  local f = false
  for i = 1, m do
    local x, y = io.read("*n", "*n")
    if x == sx and (sy - y) * (ty - y) < 0 then
      f = true
    end
  end
  local ret = mab(sy - ty) * 100
  if f then ret = ret - 20 + 10 * pi end
  printformat(ret)
  os.exit()
elseif sy == ty then
  local f = false
  for i = 1, m do
    local x, y = io.read("*n", "*n")
    if y == sy and (sx - x) * (tx - x) < 0 then
      f = true
    end
  end
  local ret = mab(sx - tx) * 100
  if f then ret = ret - 20 + 10 * pi end
  printformat(ret)
  os.exit()
end

local invmode = false
if tx < sx and ty < sy then
  sx, sy, tx, ty = tx, ty, sx, sy
elseif tx < sx then
  invmode = true
  sx, tx = -sx, -tx
elseif ty < sy then
  invmode = true
  sx, sy, tx, ty = tx, ty, sx, sy
  sx, tx = -sx, -tx
end
local t = {}
for i = 1, m do
  local x, y = io.read("*n", "*n")
  if invmode then x = -x end
  if sx <= x and x <= tx and sy <= y and y <= ty then
    table.insert(t, {x, y})
  end
end
local inf = 1000000007
local len = {}
for i = 1, #t do
  len[i] = inf
end
table.sort(t, function(a, b) return a[2] < b[2] end)
for i = 1, #t do
  local x = t[i][1]
  local lb = lower_bound(len, x)
  if x < len[lb] then
    len[lb] = x
  end
end
local fountain_count = 0
for i = 1, #t do
  if len[i] < inf then
    fountain_count = i
  else
    break
  end
end
local ret = (ty + tx - sy - sx) * 100
if fountain_count == 1 + math.min(tx - sx, ty - sy) then
  ret = ret - (fountain_count - 1) * (20 - 5 * pi) + 10 * pi - 20
else
  ret = ret - fountain_count * (20 - 5 * pi)
end
printformat(ret)