#!/usr/bin/env luajit
require("utils")
require("grid")

local f = io.open(arg[3])
local line = f:read("*l")
local g = grid(0, 0, #line, 0)
local r = 0
while line ~= nil do
	g:grow()
	local c = 0
	for char in chars(line) do
		g:set(r, c, char)
		c = c + 1
	end
	line = f:read("*l")
	r = r + 1
end

local changed = true
local step = 0
while changed do
	changed = false
	step = step + 1

	for r = g.top, g.bottom do
		for c = g.left, g.right do
			if g:get(r, c) == ">" and g:get(r, (c + 1) % g.width) == "." then
				g:set(r, c, ">>")
			end
		end
		for c = g.left, g.right do
			if g:get(r, c) == ">>" then
				changed = true
				g:set(r, c, ".")
				g:set(r, (c + 1) % g.width, ">")
			end
		end
	end

	for c = g.left, g.right do
		for r = g.top, g.bottom do
			if g:get(r, c) == "v" and g:get((r + 1) % g.height, c) == "." then
				g:set(r, c, "vv")
			end
		end
		for r = g.top, g.bottom do
			if g:get(r, c) == "vv" then
				changed = true
				g:set(r, c, ".")
				g:set((r + 1) % g.height, c, "v")
			end
		end
	end
end
print(step)