View Code of Problem 18

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner=new Scanner(System.in);
        while (scanner.hasNext()){
            int n=Integer.parseInt(scanner.nextLine());
            if(n==0||n==1||n==2){
                System.out.print(0);
            }
            if(n==3){
                System.out.print(1);
            }
            if(n==4){
                System.out.print(2);
            }
            int[] dp=new int[2*n];
            dp[0]=0;
            dp[1]=0;
            dp[2]=0;
            dp[3]=1;
            dp[4]=2;
            int x=2;
            for(int i=5;i<=n;i++){
                dp[i]=dp[i-1]+x;
                if(i%2==0){
                    x++;
                }
            }
            System.out.println(dp[n]);
        }
    }
}