local mfl = math.floor
local function getgcd(x, y)
  while 0 < x do
    x, y = y % x, x
  end
  return y
end

local function getlcm(x, y)
  local gcd = getgcd(x, y)
  return mfl(x / gcd) * y
end

local n, m = io.read("*n", "*n")
local x, _y = {}, 0
for i = 1, m do
  x[i], _y = io.read("*n", "*n")
end
local t = {}
for i = 1, n do
  local p = i
  for j = 1, m do
    if x[j] == p then
      p = p + 1
    elseif x[j] + 1 == p then
      p = p - 1
    end
  end
  t[i] = p
end

local function solve(a)
  local c = 1
  local p = t[a]
  while p ~= a do
    c = c + 1
    p = t[p]
  end
  return c
end

local lcm = 1
for i = 1, n do
  lcm = getlcm(lcm, solve(i))
end
print(lcm)