package codeup100;

import java.io.BufferedReader;

import java.io.IOException;

import java.io.InputStreamReader;

import java.util.Scanner;

public class c1080 {

public static void main(String[] args) throws IOException {

//sol1 Memory 14952 Runtime 113

/*

Scanner sc = new Scanner(System.in);

int num = sc.nextInt();

sc.close();

int sum = 0;

int i;

for(i = 1; sum < num; i++){

sum += i;

}

System.out.println(i-1);

*/

//sol2

// Using sc.close() : Memory 14348 Runtime 114

// Not using sc.close() : Memory 14312 Runtime 112

/*

Scanner sc = new Scanner(System.in);

int sum = sc.nextInt();

sc.close();

int tempSum = 0;

int i = 0;

for(i=0; tempSum < sum; i++){

tempSum += i;

if(tempSum >= sum) break;

}

System.out.println(i);

*/

//sol3 : use BufferReader

//Memory 11128 Runtime 66

BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

int sum = Integer.parseInt(br.readLine());

int tempSum = 0;

int j = 0;

for(j=0; tempSum < sum; j++){

tempSum += j;

if(tempSum >= sum) break;

}

System.out.println(j);

}

}