using System.Console;
public class Test
{
	public static Main() : void
	{
		mutable f = ReadLine();
		mutable x = 0;
		mutable y = 1;
		for(mutable i = 99; i >= 0; i--){
			if(f[i] == '1'){
				x = x+y;
			}
			else{
				x = x;
			}
			y *= 2;
		}
		WriteLine(x);
	}
}