The "the given serial cable" is a bog standard miniUSB to USB-A cable.
This information belongs in your Question - as does ALL technical detail.
The reference to "Serial Cable" is misleading the cable is USB; the serial interface is on the Arduino - no additional serial interface is needed. (It is technically possible to connect the Pi ...
analogRead a returns a float.. and the print() was probably getting confused too.
Leave out the int inputPinA = A0; because you only need to put A0 in the AnalogRead.
Make int pin = 0; a float, or better use float pin_value = 0.0; for clarity
Then the stuff in your loop becomes:
pin_value = analogRead(A0); Serial.println(pin_value);