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문제

In Manhattan, there are streets x = i and y = i for each integer i. It is known that both Snuke’s house and Smeke’s house are on streets, and the Euclidean distance between them is exactly d. Compute the maximal possible distance between their houses when they travel along streets.

입력

The input contains one number d.

  • 0 < d ≤ 10
  • d contains exactly three digits after the decimal point.

출력

Print the answer. The answer is considered to be correct if its absolute or relative error is at most 10−9.

예제 입력 1

1.000

예제 출력 1

2.000000000000

예제 입력 2

2.345

예제 출력 2

3.316330803765