<?php
/**
 * Auto-generated code below aims at helping you parse
 * the standard input according to the problem statement.
 **/

fscanf(STDIN, "%d",
    $n // the number of adjacency relations
);

class Node 
{
    protected $children = [];
    
    protected $parent = null;
    
    public function addChild(Node $node) 
    {
        $node->setParent($this);
        $this->children[] = $node;
    }
    
    public function getChildren() 
    {
        return $this->children;
    }
    
    public function setParent(Node $node) 
    {
        $this->parent = $node;    
    }
    
    public function getParent()
    {
        return $this->parent;
    }
}

class Nodes
{
    protected static $nodes = [];
    
    public static function addNode($key, Node $node) 
    {
        self::$nodes[$key] = $node;
    }
    
    public static function get($key) 
    {
        return isset(self::$nodes[$key]) ? self::$nodes[$key] : null;
    }
    
    public static function getNodes() 
    {
        return self::$nodes;
    }
}

$rootNode = null;

for ($i = 0; $i < $n; $i++)
{
    fscanf(STDIN, "%d %d",
        $xi, // the ID of a person which is adjacent to yi
        $yi // the ID of a person which is adjacent to xi
    );
    
    $parent = Nodes::get($xi);
    $child = Nodes::get($yi);
    
    if (null === $parent) {
        $parent = new Node();
        Nodes::addNode($xi, $parent);
        
        if ($rootNode === null) {
            $rootNode = $parent;
        }
    }
    
    if (null === $child) {
        $child = new Node();
        Nodes::addNode($yi, $child);
    }
    
    $parent->addChild($child);
}

$depth = 0;

foreach (Nodes::getNodes() as $k => $node) {
    if ($node->getChildren()) {
        continue;
    }
    
	$d = 0;
    $p = $node->getParent();

    while ($p) {
        $d++;
        $p = $p->getParent();
    }

    if ($d > $depth) {
        $depth = $d;
    }
}
// Write an action using echo(). DON'T FORGET THE TRAILING \n
// To debug (equivalent to var_dump): error_log(var_export($var, true));

echo("$depth\n"); // The minimal amount of steps required to completely propagate the advertisement
?>