[백준] 1789번 수들의 합

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
    	
    	Scanner kb = new Scanner(System.in);
    	
    	long s = kb.nextLong();
    	long sum = 0;
    	long add = 1;
    	
    	
    	while(true) {
    		
    		sum += add;
    		
    		if(sum>s) {
    			break;
    		}
    		
    		add+=1;
    	}
    	
    	System.out.println(add-1);
    }
}