100562: [AtCoder]ABC056 C - Go Home

Memory Limit:256 MB Time Limit:2 S
Judge Style:Text Compare Creator:
Submit:0 Solved:0

Description

Score : $200$ points

Problem Statement

There is a kangaroo at coordinate $0$ on an infinite number line that runs from left to right, at time $0$. During the period between time $i-1$ and time $i$, the kangaroo can either stay at his position, or perform a jump of length exactly $i$ to the left or to the right. That is, if his coordinate at time $i-1$ is $x$, he can be at coordinate $x-i$, $x$ or $x+i$ at time $i$. The kangaroo's nest is at coordinate $X$, and he wants to travel to coordinate $X$ as fast as possible. Find the earliest possible time to reach coordinate $X$.

Constraints

  • $X$ is an integer.
  • $1≤X≤10^9$

Input

The input is given from Standard Input in the following format:

$X$

Output

Print the earliest possible time for the kangaroo to reach coordinate $X$.


Sample Input 1

6

Sample Output 1

3

The kangaroo can reach his nest at time $3$ by jumping to the right three times, which is the earliest possible time.


Sample Input 2

2

Sample Output 2

2

He can reach his nest at time $2$ by staying at his position during the first second, and jumping to the right at the next second.


Sample Input 3

11

Sample Output 3

5

Input

题意翻译

在0秒的时候有一只袋鼠在左右无限长的数轴上的原点上。在i-1到i的时间内,袋鼠可以选择不动,也可以向任意方向跳i个单位长度。也就是说,如果袋鼠在坐标x,时间i-1到i的时候,可以存在x-i,x,x+i三点之中。袋鼠的家在坐标X。袋鼠想尽快移动到它家。求袋鼠到达家的时间的最小值。 输入格式: 输入由标准输入以下列格式给出:$ X $ 输出: 袋鼠到达坐标的最早时间

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