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

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

n = lltonumber(io.read())
r = 0LL
if n <= 3LL then
  r = n
else
  r = 3LL + 5LL * (n - 3LL)
end
r = tostring(r):gsub("LL", "")
print(r)