<?php

$firstString = explode(" ", trim(fgets(STDIN)));
$secondString = explode(" ", trim(fgets(STDIN)));

$rightCount = 0;
$leftCount = 0;

$shorter = min(count($firstString), count($secondString));


while ($rightCount < count($firstString) && $rightCount < count($secondString)) {
    if ($firstString[count($firstString) - $rightCount - 1] == $secondString[count($secondString) - $rightCount - 1]) {
        $rightCount++;
    }
    else break;
}

while ($leftCount < count($firstString) && $leftCount < count($secondString)) {
    if ($firstString[$leftCount] == $secondString[$leftCount]) {
        $leftCount++;
    }
    else break;
}

if ($rightCount > $leftCount) {
    echo $rightCount;
} else {
    echo $leftCount;
}
?>