boj_1789.java

package greedy;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class boj_1789 {
    public static void main(String[] args) throws IOException {
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        long s=Long.parseLong(br.readLine());
        long sum=0;
        int cnt=0;

        for(int i=1;;i++){
            if(sum>s) break;
            sum+=i;
            cnt++;
        }
        System.out.println(cnt-1);
        br.close();
    }
}