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Background

Special for beginners, ^_^

Description

输入一个正整数 n ，输出一个满足条件的最小的正整数 k ，使得 1+2+...+k≥n

Format

Input

输入一个数字n

Output

输出满足条件的k

Samples

12

5

100128

447

Limitation

1 ≤ N ≤ 10 ^9