package xiecheng;

import java.util.ArrayList;

import java.util.Arrays;

import java.util.List;

import java.util.Scanner;

import java.util.stream.Collectors;

public class Main2 {

static class Time implements Comparable<Time> {

int id;

String start;

String end;

public boolean compute(String A) {

return A.compareTo(start) > 0 && end.compareTo(A) > 0;

}

@Override

public String toString() {

return String.valueOf(id);

}

@Override

public int compareTo(Time o) {

return this.id - o.id;

}

}

public static void main(String[] args) {

Scanner in = new Scanner(System.in);

int N = Integer.parseInt(in.nextLine());

String A = in.nextLine();

List<Time> times = new ArrayList<>(N);

for (int i = 0; i < N; i++) {

Time time = new Time();

String[] t = in.nextLine().split(" ");

// System.out.println(t[0]+" "+t[1]+" "+t[2]);

time.id = Integer.parseInt(t[0]);

time.start = t[1];

time.end = t[2];

times.add(time);

}

in.close();

// System.out.println(times);

int[] result = new int[N];

int i = 0;

for (Time time : times) {

if (time.compute(A)) {

result[i] = time.id;

i++;

}

}

if (result[0] == 0) {

System.out.println("null");

}else {

Arrays.sort(result);

for (int j = 0; j < result.length; j++) {

if (result[j] > 0) {

System.out.println(result[j]);

}

}

}

}

}

//10

//20180602

//1001 20180103 20180100

//1001 20180103 20180101

//1001 20180103 20180102

//1001 20180103 20180607

//1001 20180103 20180104

//1001 20180103 20180105

//1001 20180103 20180106

//1001 20180103 20180107

//1001 20180103 20180108

//1003 20180103 20180603