#include <iostream>
#include <fstream>

#define INPUT_FILE "check.in"
#define OUTPUT_FILE "check.out"

using namespace std;

struct tree {
    int value, left, right;
};

string check(tree *Tree, int index) {
    string result = "YES";

    if (Tree[index].left - 1 > 0) {
        if (Tree[index].value > Tree[Tree[index].left - 1].value) {
            result = check(Tree, Tree[index].left - 1);
        } else result = "NO";
    }

    if (Tree[index].right - 1 > 0) {
        if (Tree[index].value < Tree[Tree[index].right - 1].value) {
            result = check(Tree, Tree[index].right - 1);
        } else result = "NO";
    }

    return result;
}

int main(int argc, const char * argv[]) {

    ifstream inputFile(INPUT_FILE);
    ofstream outputFile(OUTPUT_FILE);

    int n;

    inputFile >> n;

    if (n > 0) {

        tree *Tree = new tree[n];

        for (int i = 0; i < n; i++) {
            inputFile >> Tree[i].value >> Tree[i].left >> Tree[i].right;
        }

        outputFile << check(Tree, 0);

    } else {
        outputFile << "YES";
    }

    inputFile.close();
    outputFile.close();

    return 0;
}