蓝桥杯、入门训练、序列求和

import java.util.*;

public class Main{

public static void main(String[] args) {
Scanner s = new Scanner(System.in);
long n = s.nextInt();
long result = 0;
if(n%2==0){ //如果n为偶数，结果为n/2倍的n+1
result = (n/2+n/2+1)*n/2;
}else{ //如果n为奇数，结果为n/2倍的处于中间那个数加上它本身
result = n/2*(n/2+1)+n/2+1;
}
System.out.println(result);
}


}