#include <string>
#include <algorithm>

class Implode
{
	public:
		Implode(const std::string delim) : str(""), delim(delim);
		void operator()(const std::string& s);
		std::string getString() { return str; };
	private:
		std::string str;
		std::string delim;
}

Implode::operator()(const std::string& s)
{
	str += s + delim;
}

std::string infixToPostfix(const std::string& expr)
{
	std::string::size_type p, q, r;
	p = q = r = 0;

	std::vector<string> numbers;
	std::vector<string> operators;

	// Find numbers
	while(p != std::string::npos)
	{
		q = expr.find_first_of("0123456789.", p);
		r = expr.find_first_not_of("0123456789.", q);
		numbers.push_back(expr.substr(q,r-q));
		q = expr.find_first_of("+-*/%", r);
		operators.push_back(expr.substr(q,1));
		p = q;
	}

	// Merge into string
	Implode imp(" ");
	for_each(numbers.begin(), numbers.end(), imp);
	for_each(operators.begin(), operators.end(), imp);

	return imp.getString();
}