adding number in android using kotlin : Hello guyys i'm new here

I am trying to add numbers with 3 edittexts and i want to display it on text view with a calculate button but there's something wrong with kotlin code as I'm newbie 

here's my code


class Add : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_adsense)
       var input_num1 = num1
        var input_num2 = numm2
       var input_num3 = num3

        result.setOnCLickListener {
            var result = input_num1.toStrubg()?.toLong() +  input_num2.toStrubg()?.toLong() + input_num3.toLong()?.toString()
        }


    }

}


    <TextView
        android:id="@+id/textView"
        android:textSize="20dp" />

    <EditText
        android:id="@+id/num1"
        android:inputType="number" />

    <TextView
        android:id="@+id/textView2"
        android:textSize="20dp" />

    <EditText
        android:id="@+id/num2"
        android:inputType="numberDecimal" />

    <TextView
        android:id="@+id/textView3"
        android:textSize="20dp" />

    <EditText
        android:id="@+id/num3"
        android:inputType="numberDecimal" />

    <TextView
        android:id="@+id/result"
        android:textSize="20dp"
        android:text="Result" />

    <Button
        android:id="@+id/Calculate"
        android:onClick="Calculate"
        android:text="Calculate"
        android:textSize="20dp" />

</LinearLayout>
