ac

import org.omg.CORBA.INTERNAL;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.*;

class TreeNode{
    TreeNode left;
    TreeNode right;
    int val;

    public TreeNode(int val) {
        this.val = val;
        left = null;
        right = null;
    }
}

public class Main {
    public static Scanner sc = new Scanner(System.in);

    public static BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));

    public static long mod = (long) Math.pow(2, 29);

    public static void main(String[] args) throws Exception {
        String line;
        String[] strArr;
        line = reader.readLine();
        strArr = line.split(" ");
        int n = Integer.valueOf(strArr[0]);
        int rootVal = Integer.valueOf(strArr[1]);
        Map<Integer, TreeNode> mp = new HashMap<>(n);
        for (int i = 0; i < n; i++) {
            line = reader.readLine();
            strArr = line.split(" ");
            int val = Integer.valueOf(strArr[0]);
            int leftVal = Integer.valueOf(strArr[1]);
            int rightVal = Integer.valueOf(strArr[2]);

            if (!mp.containsKey(val)) {
                mp.put(val, new TreeNode(val));
            }
            if (leftVal != 0) {
                if (!mp.containsKey(leftVal)) {
                    mp.put(leftVal, new TreeNode(leftVal));
                }
                mp.get(val).left = mp.get(leftVal);
            }
            if (rightVal != 0) {
                if (!mp.containsKey(rightVal)) {
                    mp.put(rightVal, new TreeNode(rightVal));
                }
                mp.get(val).right = mp.get(rightVal);
            }
        }
        TreeNode root = mp.get(rootVal);
        System.out.println(getMaxLen(root));
    }


    static int getMaxLen(TreeNode root){
        if(root == null){
            return 0;
        }
        int leftLen = getMaxLen(root.left);
        int rightLen = getMaxLen(root.right);
        int rootMaxLen =  getMaxSinglePath(root.left) +  getMaxSinglePath(root.right) + 1;
        return Math.max(Math.max(leftLen, rightLen), rootMaxLen);
    }

//    static int getMaxLenBySingle(int leftMaxLen, int rightMaxLen){
//        if(leftMaxLen == 0 && rightMaxLen == 0){
//            return 1;
//        }else if(rightMaxLen == 0){
//            return leftMaxLen;
//        }else if(leftMaxLen == 0){
//            return rightMaxLen;
//        }else {
//            return leftMaxLen + rightMaxLen - 1;
//        }
//    }

    // 以 root 为节点的，左边 或者 右边最大单路径
    static int getMaxSinglePath(TreeNode root){
        if(root == null){
            return 0;
        }
        int leftPath = getMaxSinglePath(root.left);
        int rightPath = getMaxSinglePath(root.right);
        return Math.max(leftPath, rightPath) + 1;
    }

}
/*
         1
      /     \
     2        3
    / \      / \
   4  5     6  7
              /
             8

8 1
1 2 3
2 4 5
4 0 0
5 0 0
3 6 7
6 0 0
7 8 0
8 0 0

6

         1
      /     \
     2        3
    / \      / \
   4  5     6  7

7 1
1 2 3
2 4 5
4 0 0
5 0 0
3 6 7
6 0 0
7 0 0

5
 */