javascript:

var num = 1;

var str = parseInt(num).toString(2),n;

n = /10/.test(str) ? str.replace(/^(\d*)10(0*)$/g,function($,b,c,d){return b+"01"+d}):

        str.replace(/^1(1*)$/g,function($,b){return "10"+b});

console.log(parseInt(n,2));