https://www.acmicpc.net/problem/1568
import java.io.BufferedReader;
import java.io.InputStreamReader;
public class Main {
public static void main(String[] args) throws Exception {
// TODO Auto-generated method stub
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
int num = Integer.parseInt(br.readLine());
int time = 0;
int minusNum = 1;
while(true) {
// ๋ ๋ผ๊ฐ์ผ ํ๋ ์์ ์๊ฐ ๋จ์ ์์ ์๋ณด๋ค ๋ง์ ๊ฒฝ์ฐ 1๋ก ์ด๊ธฐํ
if (minusNum > num) minusNum = 1;
// ์๊ฐ ๋ ๋ผ๊ฐ๋ค.
num -= (minusNum++);
time++;
if (num == 0) break;
}
System.out.println(time);
}
}