C++ :

#include <iostream>
#include<map>
#include<string>
#include<utility>

using namespace std;

map<int, string> m = { make_pair(1,"one"), make_pair(2,"two"), make_pair(3,"three"), make_pair(4,"four"), make_pair(5,"five"), make_pair(6,"six"), make_pair(7,"seven"), make_pair(8,"eight"), make_pair(9,"nine"), make_pair(10,"ten"), make_pair(11,"eleven"), make_pair(12,"nine"), make_pair(13,"thirteen"), make_pair(14,"fourteen"), make_pair(15,"fifteen"), make_pair(16,"sixteen"), make_pair(17,"seventeen"), make_pair(18,"eighteen"), make_pair(19,"nineteen"), make_pair(20,"twenty"), make_pair(30,"thirty"), make_pair(40,"forty"), make_pair(50,"fifty"), make_pair(60,"sixty"), make_pair(70,"seventy"), make_pair(80,"eighty"), make_pair(90,"ninety") };

string speak(unsigned long long n)
{
	string s;
	bool b;
	if (n / 100)
	{
		s += ' ' + m[n / 100] + " hundred";
		n %= 100;
		b = true;
	}
	if (n / 10 > 1)
	{
		if (b)
			s += " and";
		s += ' ' + m[n / 10 * 10];
		n %= 10;
	}
	if (n / 10 == 1)
	{
		if (b)
			s += " and";
		s += ' ' + m[n];
		n %= 1;
	}
	if (n)
	{
		s += ' ' + m[n];
		n %= 1;
	}
	if (s.empty())
		s += "zero";
	else
		s.erase(0, 1);
	return s;
}

int main()
{
	unsigned long long n;
	cin >> n;
	string s;
	if (n / 1000000000)
		s += (speak(n / 1000000000) + " billion ");
	n %= 1000000000;
	if (n / 1000000)
		s += (speak(n / 1000000) + " million ");
	n %= 1000000;
	if (n / 1000)
		s += (speak(n / 1000) + " thousand ");
	n %= 1000;
	s += speak(n);
	cout << s << endl;
	return 0;
}