Student Academy

<?php

$n = intval(readline());
$studentGrades = [];

for ($i = 0; $i < 2 * $n; $i++) {
    $input[] = readline();
    if ($i === 0 || $i % 2 === 0) {
        if (!key_exists($input[$i], $studentGrades)) {
            $studentGrades[$input[$i]] = [];
        }
    } else {
        array_push($studentGrades[$input[$i - 1]], floatval($input[$i]));
    }
}

foreach ($studentGrades as $student => $grade) {
    $studentGrades[$student] = array_sum($studentGrades[$student]) / count($studentGrades[$student]);
}

arsort($studentGrades);

foreach ($studentGrades as $student => $grade) {
    if ($grade >= 4.50) {
        printf("%s -> %.2f\n", $student, $grade);
    }
}