Problem:
Score : 400 points

Problem Statement

You are given a sequence A_1, A_2, ..., A_N and an integer K.

Print the maximum possible length of a sequence B that satisfies the following conditions:

B is a (not necessarily continuous) subsequence of A.

For each pair of adjacents elements of B, the absolute difference of the elements is at most K.

Constraints

1 \leq N \leq 300,000

0 \leq A_i \leq 300,000

0 \leq K \leq 300,000

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N K
A_1
A_2
:
A_N

Output

Print the answer.

Sample Input 1

10 3
1
5
4
3
8
6
9
7
2
4

Sample Output 1

7

For example, B = (1, 4, 3, 6, 9, 7, 4) satisfies the conditions.

It is a subsequence of A = (1, 5, 4, 3, 8, 6, 9, 7, 2, 4).

All of the absolute differences between two adjacent elements (|1-4|, |4-3|, |3-6|, |6-9|, |9-7|, |7-4|) are at most K = 3.

Solution in C# (.NET Core 3.1.201) (judge verdict: Wrong Answer)

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;

namespace atcoder
{
    public class Program
    {
        public static void Main(string[] args)
        {
            var buffer = Console.ReadLine().Split();
            var N = int.Parse(buffer[0]);
            var K = int.Parse(buffer[1]);
            var list = new List<int>();
            for (int i = 0; i < N; i++)
                list.Add(int.Parse(Console.ReadLine()));

            var max = int.MinValue;
            for (int i = 1; i < N; i++)
            {
                if (Math.Abs(list[i - 1] - list[i]) <= K)
                {
                    var tmp = Count(i - 1, N, list, K);
                    if (max < tmp) max = tmp;
                }
            }

            Console.WriteLine(max);
        }

        static int Count(int i, int N, List<int> list, int K)
        {
            var ans = 1;
            for (; i < N; i++)
            {
                int up = 0;
                for (int j = i + 1; j < N; j++)
                {
                    if (Math.Abs(list[i] - list[j]) <= K)
                    {
                        Console.WriteLine(Math.Abs(list[i] - list[j]));
                        ans++;
                        break;
                    }
                    up++;
                }
                i += up;
            }

            return ans;
        }
    }
}