import java.util.Scanner;
public class Main {
public static void main
(String[] args
) {
Scanner sc
= new Scanner
(System.
in); int n = sc.nextInt();
//방이 생성되는 라운드 체크
int num = 1;
//생성되는 방 수 체크, 중앙 제외하고 2부터 시작
int beeRoom = 2;
boolean isValue = false;
while(true)
{
//처음 주변에 6개방 2번째 주변에 12개, 3번째 주변에 18개씩 증가함
int end = num * 6;
for(int i=0;i<end;i++)
{
if(beeRoom==n)
{
isValue = true;
break;
}else {
beeRoom++;
}
}
if(isValue==true)
break;
else {
num++;
}
}
//라운드 수 + 1 만큼이 최소 개수의 방을 지나서 가는 경우다.
}
}
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