#include <iostream>
#include <vector>
#include <fstream>
using namespace std;

struct node {
    int key;
    vector < int > kids;
};

vector < node > arr;

bool dfs(vector < node > &arr, int key, int pos, int left, int right)
{
    if (key == -1)
    {
        return true;
    }
    if (key > right || key < left)
    {
        return false;
    }
    if (arr[pos].kids[1] == -1 && arr[pos].kids[0] ==-1)
    {
        return true;
    }
    int leftchild, rightchild, leftpos, rightpos;
    if (arr[pos].kids[0] != -1)
    {
        leftchild = arr[arr[pos].kids[0]].key;
    } else {
        leftchild = -1;
    }
    leftpos = arr[pos].kids[0];
    if (arr[pos].kids[1] != -1)
    {
        rightchild = arr[arr[pos].kids[1]].key;
    } else {
        rightchild = -1;
    }
    rightpos = arr[pos].kids[1];

    return (dfs(arr, leftchild, leftpos, left, key) && dfs(arr, rightchild, rightpos, key, right));
}

int main()
{
    ifstream fin("check.in");
    ofstream fout("check.out");

    int n;
    fin >> n;
    arr.resize(n);
    int key, num1, num2;
    if (n == 0)
    {
        fout << "YES";
    } else {
        for (int i = 0; i < n; i++)
        {
            fin >> key;
            fin >> num1 >> num2;
            arr[i].key = key;
            arr[i].kids.push_back(num1 - 1);
            arr[i].kids.push_back(num2 - 1);
        }

        if (dfs(arr, arr[0].key, 0, INT_MIN, INT_MAX))
        {
            fout << "YES";
        } else {
            fout << "NO";
        }
    }

}