import java.util.*;
import java.lang.*;
import java.io.*;

class Main
{
	static Scanner sc = new Scanner(System.in);
	
	public static void main (String[] args) throws java.lang.Exception
	{
		double mul = 1;
		double x;
		while(sc.hasNext()){
			x = sc.nextDouble();
			if(x < 0){
				break;
			}
			mul *= x;
		}
		System.out.println(mul);
	}
}