RE: Connect your Bot to the World - XML, JSON, Web Services, HTML Scraping, Twitter, Facebook, Telegram, Email

I want to use substring to take string in form like "My last answer is this" then applying s.substring(3,s.size()) it returns "last answer is this" but my concerns is If I used previous last answer to substring it wont work. I have user 
var a = conversation.getLast(#input, 1).input ; //The string is: My last answer is this

var  s = a.substring(3,a.size());

returns "";

Even if i used to find size of that last answer it returns only 3 using a.size().

& one more I have in trouble, I want to post some data to request service url how it could be done if url is in post method?