local ffi = require("ffi")
local C = ffi.C
ffi.cdef[[
long long atoll(const char*);
]]

local function lltonumber(str)
  return C.atoll(str)
end

local n = io.read("*n", "*l")
local s = io.read()
local a = {}
for w in s:gmatch("%d+") do
  table.insert(a, lltonumber(w))
end
table.sort(a)
local len = {}
for i = 1, n do
  len[i] = 0
end
for i = n - 1, 1, -1 do
  if a[i] + 2LL == a[i + 1] then
    len[i] = len[i + 1] + 1
  elseif i + 2 <= n and a[i] + 2LL == a[i + 2] then
    len[i] = len[i + 2] + 1
  else
    len[i] = 0
  end
end
local ret = n
for i = 1, n - 1 do
  if a[i] + 1LL == a[i + 1] then
    ret = ret + 1 + len[i + 1]
  end
end
print(ret)