<?php
$s = trim(fgets(STDIN));

if (substr_count($s, "3") == strlen($s) - 1 && substr($s, 0, 1) == "1") {
    if (strlen($s) > 1) {
        echo substr_count($s, "3", 1).PHP_EOL;
    } else {
        echo "-1".PHP_EOL;
    }
}
?>