public class IsArrayInWaveFrom {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String input = scanner.nextLine();
        String [] arr = input.split(" ");
        Integer [] arryInt = new Integer[arr.length];
        String wave ="";

        for (int i = 0; i < arr.length ; i++) {
            arryInt[i] = Integer.parseInt(arr[i]); } // filling the Int array
        for (int i = 1 ; i < arryInt.length; i+=2) {
            for (int j = 2; j < arryInt.length; j++) {
                if (arryInt[i - 1] > arryInt[i]) {
                    if (arryInt[j - 1] < arryInt[j]) {

                        wave = "Yes";

                    }

                } else {
                wave = "No";
            }
            }
        }

        System.out.println(wave);
        }

    }