import java.util.Scanner;
public class SumDemo {
public static void main (String args[]){
Scanner s=new Scanner(System.in);
System.out.println("求
正整数以内的偶数和。。。");
System.out.println("请输入一位正整数");
int n=s.nextInt();
int m=n/2+1;
int sum=0;
do {
sum=(m-1)*(m);
} while (sum==n);
System.out.println(sum);
}
}