Imports System
Public Class Test
	Public Shared Function bin2dec(bin As String) As Integer
		Dim dec,i,j As Integer
		Dim ch as String
		dec=0
		j=1
		for i=len(bin) to 1 step -1
			ch=mid(bin,i,1)
			if ch="1" then 
				dec=dec+j
			else if ch<>"0"
				Console.WriteLine("invalid input")
				end
			end if
			j=j*2
		next
		Return dec
	End Function
 
	Public Shared Sub Main()
		Console.WriteLine(bin2dec(Console.ReadLine()))
	End Sub
End Class
 

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