function padding(num, sep) {
var numarr = num['toString']().split('')
var numarrLen = numarr.length
var out = []
for (;numarrLen--;) {
  var num = numarr[numarrLen]
  out.unshift(num)
  if (numarr.length !== numarrLen && num % 3 === 0) out.unshift(sep)
}
return out.join('')
}