Baekjoon #1789

#include<bits/stdc++.h>

using namespace std;
typedef long long ll;

ll S;
bool chk(ll n){ return n*(n+1)/2 > S; }

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    cin >> S;
    ll l = 1, r = 93000; // sqrt(4294967295 * 2)
    while(l <= r){
        ll mid = (l + r) / 2;
        if(chk(mid))r = mid - 1;
        else l = mid + 1;
    }
    cout << r;
}

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

public class Main {
	public static void main(String[] args) throws IOException{
		FastReader rd = new FastReader();
		
		long size = rd.nextLong();
		
		long count = 1, sum = 0;
		while(size >= sum) {
			sum += count;
			count++;
		}
		
		System.out.print(count - 2);
	}
	
	static class FastReader {
        BufferedReader br;
        StringTokenizer st;

        public FastReader() {
            br = new BufferedReader(new InputStreamReader(System.in));
        }

        String next() {
            while(st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                }
                catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }

        int nextInt() { return Integer.parseInt(next()); }
        long nextLong() { return Long.parseLong(next()); }
        double nextDouble() { return Double.parseDouble(next()); }
        String nextLine() {
            String str = "";
            try {
                str = br.readLine();
            }
            catch (IOException e) {
                e.printStackTrace();
            }
            return str;
        }
    }
}