On all Arduino except the DUE, `attachInterrupt` does not use the pin number as first argument but the interrupt number, which is diferent:

    void attachInterrupt(uint8_t interrupt, void (*ISR)(void), int mode);

As documented on [Arduino reference][1], for an Arduino UNO, the mapping is as follows:

 - interrupt 0 -> pin 2
 - interrupt 1 -> pin 3

So just change the code in `setup()` to:

    attachInterrupt(0, inter, CHANGE);

And that should work for pin 2.

  [1]: http://arduino.cc/en/Reference/AttachInterrupt