
Module Module1
    Sub main()
        Dim userInput As String, userInput2 As String
        Dim total As Long

        ' データの入力
        userInput = Console.ReadLine()
        userInput2 = Console.ReadLine()

        For i = 1 To Len(userInput)
            If Mid(userInput, i, 1) <> Mid(userInput2, i, 1) Then
                'Console.WriteLine(Mid(userInput, i, 1) & ", " & Mid(userInput2, i, 1) & ", " & userInput)

                userInput = Mid(userInput, 1, i - 1) & Mid(userInput2, i, 1) & Mid(userInput, i + 1, Len(userInput))
                total = total + 1

            End If
        Next
        '' 処理結果を返す
        Console.WriteLine(total)
    End Sub
End Module