local n = io.read("*n")
local a = {}
for i = 1, n do
  a[i] = io.read("*n")
end
table.sort(a)
local f = true
for i = 1, n - 1 do
  if a[i + 1] - a[i] == 1 then f = false break end
end
print(f and 1 or 2)