import java.util.Scanner; public class Main { public static void main(String[] args) { Scanner scan = new Scanner(System.in); int n = scan.nextInt(); int sum = 0; int day = 0; // 1 + 2+2 + 3+3+3 + 4+4+4+4 +... //或者 1^2 + 2^2 + 3^2 + 4^2 +...,不过要区分每...