<?php

$abc = "A???B";

calc($abc);
function calc($abc)
{
	$possibities = 1;
	$indexes = array();
	$abc = str_split($abc);
	for ($i= 0; $i < count($abc) ; $i++) {
		if ($abc[$i] == "?") {

			if ($i == 0 || $i == (count($abc) -1)) {
				$possibities = $possibities * 3;
			} else {
				if ($abc[$i - 1] != "?") {
					if ($abc[$i + 1] != "?") {
						$possibities = $possibities * 2;
					} else{
						$possibities = $possibities * 3;
					}
				} else {
					if ($abc[$i + 1] == "?") {
						$possibities = $possibities * 3;
					} else {
						$possibities = $possibities * 2;
					}

				}
			}
		}
	}

	echo $possibities;

}