题解 | #[NOIP2015]金币#

import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int k =in.nextInt();//第几天
        int sum=0;//金币数
        int t = 1;//当前金币数第几天
        int s = 1;//当前金币数
        for(int i=1;i<=k;i++){
            sum+=s;
            if(t==s){
                t=1;
                s++;
            }else{
                t++;
            }
        }
       System.out.print(sum);
    }
}