#include <iostream>
#include <vector>
#include <stack>

using namespace std;


bool is_operator(char c){
	return ((c=='+')||(c=='-')||(c=='*')||(c=='/'));
}

// assuming that expression is a well-formed postfix notations, tokens will have the list of integers and operators in order of appearance.
void Tokenize(string expression, vector<string>& tokens){

	string last_int = "";
	// expression has only characters of space, digit, or operator(+-*/)
	for (int i=0; i<expression.size(); i++)
		if (expression[i]==' '){ // we may have finished reading an integer
			if (last_int != ""){
				tokens.push_back(last_int);
				last_int = "";
			}
		}
		else if (is_operator(expression[i])){ 
			string one_char_string = " ";
			one_char_string[0]=expression[i]; // one_char_string now contains the operator
			tokens.push_back(one_char_string);
			
			// we may have finished reading an integer too
			if (last_int != ""){
                                tokens.push_back(last_int);
                                last_int = "";
                        }
		}
		else  // expression[i] is a digit
			last_int.push_back(expression[i]);	
}


int main(int argc, char**  argv ){
	vector<string> tokens;
        Tokenize("5 43 90 * -", tokens);
        for (int i=0; i<tokens.size(); i++)
                cout << tokens[i] << " ";
        cout << endl;
}