import java.util.*;

public class Main {
    //Write a program that reads a sequence of integer numbers and outputs true if the sequence is ordered
    // (in ascending or descending order), otherwise, false. Keep in mind, if a number has the same value as the following number,
    // it does not break the order.
    //
    //The sequence ends with 0. Do not consider this number as a part of the sequence.
    // The sequence always has at least one number (excluding 0).

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int number = 0;
        boolean result = true;
        List<Integer> list1 = new ArrayList<>();
        List<Integer> list2 = new ArrayList<>();

        while (scanner.hasNext()) {
            number = scanner.nextInt();
            if (number == 0) {
                break;
            }
            list1.add(number);
            list2.add(number);
        }
        if (list1.size() <= 1) {
            System.out.println("true");
        } else {
            if (list1.get(0) > list1.get(1)) {
                Collections.sort(list2, Collections.reverseOrder());
            } else {
                Collections.sort(list2);
            }

            for (int i = 0; i < list1.size(); i++) {
                if (!list1.get(i).equals(list2.get(i))) {
                    result = false;
                    break;
                }
            }
            System.out.println(result);
        }
    }
}