Mega2560 analog comparator AIN0 pin do not have a mapped pin?

I want to use Mega2560's analog comparator(two inputs--AIN0 & AIN1), Pin Mapped Table shows that AIN1 was mapped to Digital Pin 5(PWM), but AIN0 Do Not have a mapped pin,so how can i use AIN0? If anyone can give me some advise? Thanks for your help.

I have the same trouble, have you solve it?

I suspect the answer may lie in Section 25.1 of the Atmega 2560 datasheet

It is possible to select any of the ADC15:0 pins to replace the negative input to the Analog Com-

If that does not work the only solution I can see (from looking at my Mega) is to solder a wire the the AIN1 connector - not a job for someone with shaky hands.