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

public class Lisp {
	
	// Evaluate entire well-formed Lisp expression
	public double evaluateLispExpr(String input) { return -1.0; }
	
	// Evaluate simple expression of form: operator operand1 operand2...
	//	It is much easier to compute such an expression easily
	private double performOperation(Stack<String> s){ return -2.0; }
	
	public static void main(String[] args) {
		Lisp program = new Lisp();
		Scanner sc = new Scanner(System.in);
		System.out.println(program.evaluateLispExpr(sc.nextLine()));
		sc.close();
	}

}