Problem:
Score : 100 points

Problem Statement

Print the circumference of a circle of radius R.

Constraints

1 \leq R \leq 100

All values in input are integers.

Input

Input is given from Standard Input in the following format:

R

Output

Print the circumference of the circle.
Your output is considered correct if and only if its absolute or relative error from our answer is at most 10^{-2}.

Sample Input 1

1

Sample Output 1

6.28318530717958623200

Since we accept an absolute or relative error of at most 10^{-2}, 6.28 is also an acceptable output, but 6 is not.

Sample Input 2

73

Sample Output 2

458.67252742410977361942

Solution in Kotlin (1.3.71) (judge verdict: Accepted)


fun main(args: Array<String>) {
    /*readLine()で一行分の入力をString型として受け取り（"!!"でnull非許容に）
    split()で空白区切りにパースし
    map{}でInt型に変換して各変数に代入する
    */
    val (a) = readLine()!!.split(" ").map{ it.toInt() }
    
    print(a * 2 * 3.141592)
}