// A program for learning and expermenting.
//not for practical use of conversion from binary to decimal
import java.util.Scanner;
class BinaryToDecimal
{
public static void main(String args[])
{
Scanner s=new Scanner(System.in);
System.out.println("Enter a binary number:");
int n=s.nextInt();
int decimal=0,p=0;
while(n!=0)
{
decimal+=((n%10)*Math.pow(2,p));
n=n/10;
p++;
}
System.out.println(decimal);
}
}