import java.util.Stack;
import java.util.Scanner;

public class TP2E08 {

	public static void main(String[] args) {
		TP2E08 exercise = new TP2E08();
		exercise.execute();
	}

	private void execute() {
		Scanner console = new Scanner(System.in);
		System.out.print("Ingrese una expresión interfija: ");
		String interFixExpression = console.nextLine();
		System.out.println("Expresión posfija: " + toPostFix(interFixExpression));
		console.close();
	}
	
	private String toPostFix(String interFixExpression) {
		String postFixExpression = "";
		
		Stack<Character> operators = new Stack<Character>();
		
		Character c;
		for (int i = 0; i < interFixExpression.length(); ++i) {

			c = interFixExpression.charAt(i);
			if ((c >= '0') && (c <= '9')) {
				postFixExpression += c;
			} else {
				while ((operators.size() > 0) && (precedence(operators.peek()) >= precedence(c))) {
					postFixExpression += operators.pop();
				}
				operators.push(c);
			}
		}

		while (operators.size() > 0) {
			postFixExpression += operators.pop();
		}

		return postFixExpression;
	}

	private int precedence(Character operator) {
		switch(operator) {
		case '+' :
			return 1;
		case '-' :
			return 1;
		case '*' :
			return 2;
		case '/' :
			return 2;
		default :
			return 3;
		}
	}
}