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 (Python):
import numpy as np

r=int(input())
print(np.pi*2*r)

Solution (Python):
R = int(input())

enn = R * 2 * 3.14
  
print(enn)

Solution (Python):
import math
pi = math.pi
r = int(input())
print(2 * r * pi)

Solution (Python):
import math

r = int(input())

print(math.pi*r*2)

Solution (Python):
import numpy as np

R = int(input())

print(2 * R * np.pi)

Solution (Python):
import math
R = int(input())
print(2*R*math.pi)

Solution (Python):
R = float(input())

print(2*R*3.14159)

Solution (Python):
import math
r = int(input())
print(r*2*math.pi)

Solution (Python):
import math
a = int(input())
print(a * 2 * math.pi)

Solution (Python):
a = int(input())
print(2*(22/7)*a)

Solution (Python):
import math
n = int(input())
a = math.pi
print(2*n*a)

Solution (Python):
r = int(input())
x = 2*3.141592 * r
print(x)

Solution (Python):
import math
r = int(input())
print(float((r*2)* math.pi))

Solution (Python):
import math
r=int(input())
print(2*r*math.pi)

Solution (Python):
r=int(input())
print(2*r*3.1415)

Solution (Python):
R=int(input())
multiply=2*R*22/7
print(multiply)

Solution (Python):
r=int(input())

import math
print(2*r*math.pi)

Solution (Python):
print(2*3.14*int(input()))

Solution (Python):
import math
r = int(input())

R = 2*math.pi*r
print(R)

Solution (Python):
import math
r = int(input())
print(2*r*math.pi)

Solution (Python):
import math
 
r = int(input())
print(2 * math.pi * r)

Solution (Python):
import math

R = int(input())
print(R*2*math.pi)

Solution (Python):
import math

R = int(input())
print(R*2*math.pi)

Solution (Python):
r=int(input())
print(2*r*3.14)

Solution (Python):
import math

r = int(input())
print(2 * math.pi * r)

Solution (Python):
import math
print(2 * math.pi * int(input()))

Solution (Python):
from math import pi

r = int(input())

print(2 * int(r) * pi)

Solution (Python):
a=float(input())
print(a*2*3.1415926)

Solution (Python):
a=float(input())
print(a*2*3.1415926)

Solution (Python):

from collections import defaultdict, Counter
from itertools import product, groupby, count, permutations, combinations
from math import pi, sqrt
from collections import deque
from bisect import bisect, bisect_left, bisect_right
from string import ascii_lowercase
from functools import lru_cache
import sys
sys.setrecursionlimit(10000)
INF = float("inf")
YES, Yes, yes, NO, No, no = "YES", "Yes", "yes", "NO", "No", "no"
dy4, dx4 = [0, 1, 0, -1], [1, 0, -1, 0]
dy8, dx8 = [0, -1, 0, 1, 1, -1, -1, 1], [1, 0, -1, 0, 1, 1, -1, -1]


def inside(y, x, H, W):
    return 0 <= y < H and 0 <= x < W


def ceil(a, b):
    return (a + b - 1) // b


def sum_of_arithmetic_progression(s, d, n):
    return n * (2 * s + (n - 1) * d) // 2


def gcd(a, b):
    if b == 0:
        return a
    return gcd(b, a % b)


def lcm(a, b):
    g = gcd(a, b)
    return a / g * b


def solve():
    R = int(input())
    print(2 * R * pi)


def main():
    solve()


if __name__ == '__main__':
    main()

Solution (Python):
from math import pi
print(f'{2 * pi * int(input()):.5f}')

Solution (Python):
import math
pi = math.pi
R = int(input())
print(2*R*pi)

Solution (Python):
import math
R= int(input())
print(2*R*math.pi)

Solution (Python):
import math

r = int(input())

print(2*math.pi*r)

Solution (Python):
import math
R = int(input())

print(2*math.pi*R)

Solution (Python):
print(2*3.14*int(input()))

Solution (Python):
import math

r=int(input())
print(2*r*math.pi)

Solution (Python):
import math

r = int(input())
print(2 * r * math.pi)

Solution (Python):
import math
print(2 * math.pi * int(input()))

Solution (Python):
import numpy

r = int(input())

print(2 * r * numpy.pi)

Solution (Python):
import math
print(int(input())*math.pi*2)

Solution (Python):
import sys
sys.setrecursionlimit(10 ** 9)

def int1(x): return int(x) - 1
def II(): return int(input())
def MI(): return map(int, input().split())
def MI1(): return map(int1, input().split())
def LI(): return list(map(int, input().split()))
def LI1(): return list(map(int1, input().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]
def MS(): return input().split()
def LS(): return list(input())
def LLS(rows_number): return [LS() for _ in range(rows_number)]
def printlist(lst, k=' '): print(k.join(list(map(str, lst))))
INF = float('inf')







def solve():
    R = II()
    print(2 * R * 3.141592)

if __name__ == '__main__':
    solve()

Solution (Python):
import math
R = int(input())

print(2 * R * math.pi)

Solution (Python):
import math
r=int(input())
pi=math.pi
print(r*2*pi)

Solution (Python):
from collections import defaultdict as dd
from collections import deque
import bisect
import heapq
import math

def ri():
    return int(input())

def rl():
    return list(map(int, input().split()))


def solve():
    r = ri()
    print (2 * r * math.pi)






mode = 's'

if mode == 'T':
    t = ri()
    for i in range(t):
        solve()
else:
    solve()

Solution (Python):
R = int(input())
print(R * 2 * 3.1415)

Solution (Python):
r = int(input())
print(2*r*3.14)

Solution (Python):
r=int(input())
print(6.283*r)

Solution (Python):
import math
R = int(input())

print(2 * math.pi * R)

Solution (Python):
import math
r=int(input())
print(2*r*math.pi)

Solution (Python):
import math

R = int(input())
print(R * 2 * math.pi)

Solution (Python):
import math
r = int(input())
print(2 * math.pi * r)

Solution (Python):
import math
print(int(input())*2*math.pi)

Solution (Python):
from math import pi
r = int(input())

print(r*2*pi)

Solution (Python):
import math

R = int(input())
ans = (R + R) * math.pi

print(ans)

Solution (Python):


import math
print(2*int(input())*math.pi)

Solution (Python):
R =int(input())
print(R*3.14159*2)

Solution (Python):
import math
R = int(input())
print(math.pi*2*R)

Solution (Python):
r = float(input())
print(2*(22/7)*r)

Solution (Python):
import math
r=int(input())
print(math.pi*r*2)

Solution (Python):
r = int(input())

print(r * 3.141592 * 2)

Solution (Python):
R=input()
R=int(R)
print(3.1415*2*R)

Solution (Python):
print(int(input()) * 3.14159265359 * 2)

Solution (Python):
import sys
read = sys.stdin.buffer.read






def RD(): return sys.stdin.read()
def II(): return int(input())
def MI(): return map(int,input().split())
def MF(): return map(float,input().split())
def LI(): return list(map(int,input().split()))
def LF(): return list(map(float,input().split()))
def TI(): return tuple(map(int,input().split()))

from math import *


def main():
	r=II()
	print(2*r*pi)
	
	
	


	
if __name__ == "__main__":
	main()

Solution (Python):
r = int(input())
print(r*2*3.14159265359)

Solution (Python):

import math


def main():
    r = int(input())
    print(2 * r * math.pi)


if __name__ == '__main__':
    main()

Solution (Python):
import math
R = int(input())
print(2 * math.pi * R)

Solution (Python):
import math

R=int(input())
l=2*math.pi*R
print(l)

Solution (Python):
import math

r = int(input())

print(2 * r * math.pi)

Solution (Python):
import math
x = math.pi
r = int(input())
x = 2*x*r
print(x)

Solution (Python):


r = int(input())

print(r * 2 * 3.14)

Solution (Python):
import numpy as np
R= float(input())
print(2*np.pi*R)

Solution (Python):
import math

r = int(input())

print(2 * r * math.pi)

Solution (Python):
R=input()

int(R)

y=2*int(R)*3.141592653

print(y)

Solution (Python):
import numpy as np

e=input()
num=int(e)
print(num*2*np.pi)

Solution (Python):
import math
R = int(input())
print(R*2*math.pi)

Solution (Python):
import math

R = int(input())
print(2 * math.pi * R)

Solution (Python):
r = int(input())
pi = 22/7
circ = 2*pi*r
print(circ)

Solution (Python):
from math import pi

print(2 * pi * int(input()))

Solution (Python):
r = int(input())

import numpy as np
print(r*2*np.pi)

Solution (Python):
import math

r = int(input())

print(2 * math.pi * r)

Solution (Python):
R=int(input())

N=R*2*3.141592

print(N)

Solution (Python):
import math
r = int(input())
print(2*r*math.pi)

Solution (Python):
r = int(input())

print(r * 3.14159265 * 2);

Solution (Python):
import math
print(2 * int(input()) * math.pi)

Solution (Python):
import math

R=int(input())
print(R*2*math.pi)

Solution (Python):


import math

r=int(input())
print(2*r*math.pi)

Solution (Python):


import math

r=int(input())
print(2*r*math.pi)

Solution (Python):
import math
R=int(input())


print(R*math.pi*2)

Solution (Python):
import math

r=input()
a=(int)(r)*2*math.pi
print(a)

Solution (Python):
from math import pi

r = int(input())

print((r*2)*pi)

Solution (Python):
import math
r = int(input())
print(2*r*math.pi)

Solution (Python):
import math
print(2*math.pi*int(input()))

Solution (Python):
import math
R = int(input())
print(2*R*math.pi)

Solution (Python):
import math
print(int(input())*2*math.pi)

Solution (Python):
import sys
def main():
    R=int(sys.stdin.readline())
    print(6.283184*R)
if __name__=='__main__':main()

Solution (Python):
import math
n=int(input())
print(math.pi*2*n)

Solution (Python):
import numpy as np
pi = np.pi 
a=int(input())
print((a*2)*pi)

Solution (Python):
import math
n = int(input())
print(2 * n * math.pi)

Solution (Python):
r = int(input())
a = (44/7)*r
print(a)

Solution (Python):
r=int(input())
print(2*(22/7)*r)

Solution (Python):
import math

def main():

    R = input_int()

    print(R * 2 * math.pi)


def input_int():
    return int(input())


def input_ints():
    return map(int, input().split())


def input_int_list_in_line():
    return list(map(int, input().split()))


def input_int_tuple_list(n: int, q: int):
    return [tuple(map(int, input().split())) for _ in range(n)]


main()

Solution (Python):
r = int(input())

print(3.14 * r *2)

Solution (Python):
R = int(input())
a = (44/7)*R
print(a)

Solution (Python):
R = int(input())
print(2*R*3.121592)

Solution (Python):
R = int(input())
print(2*R*3.14159265)

Solution (Python):
from math import *
print(pi*2*(int(input())))

Solution (Python):
import math
a = float(input())
print(2*a*math.pi)

Solution (Python):
r = int(input())
print(3.1415*2*r)

Solution (Python):
pi = 3.141
r = int(input())
print(2*pi*r)

Solution (Python):
r = int(input())
D = 2* r
print(3.1415926535897 * D)

Solution (Python):
radius = int(input())

print(44/7*radius)

Solution (Python):
import math
print(2 * math.pi * int(input()))

Solution (Python):
import math
r=int(input())
print(2*math.pi*r)

Solution (Python):
import math
r=int(input())
c=2*r*math.pi
print(c)

Solution (Python):
import math
print(int(input()) * 2 * math.pi)

Solution (Python):
import math

r = int(input())
print(2*r*math.pi)

Solution (Python):
print(6.28*int(input()))

Solution (Python):
from math import *
print(2*pi*int(input()))

Solution (Python):
print(int(input()) * 2 * 3.14159)

Solution (Python):
import numpy as np
r = int(input())
print(2 * r * np.pi)

Solution (Python):
R = int(input())
import math
print(2*math.pi*R)

Solution (Python):
import math

r = int(input())

print(math.pi*2*r)

Solution (Python):
import math
R=int(input())
print(R*2*math.pi)

Solution (Python):
import math

R = int(input())

print(2*math.pi*R)

Solution (Python):

import math

print(int(input()) *2 * math.pi)

Solution (Python):
import math

def main():
    r = int(input())
    ans = 2 * r * math.pi
    print(ans)

if __name__ == '__main__':
    main()

Solution (Python):
def main():
  r = int(input())
    
  a = r * 2
  
  print(a * 3.14)
  
main()

Solution (Python):
import sys 
import math
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines
N = int(readline())
print(2*N*math.pi)

Solution (Python):
import math
R=int(input())
ensyu=2*math.pi*R
print(ensyu)

Solution (Python):
r = int(input())
print(2*r*3.1415)

Solution (Python):
r = int(input())

s = r * 2 * 3.14
print(s)

Solution (Python):
R = int(input())
print(R*2*3.14)

Solution (Python):
print(2*3.14*int(input()))

Solution (Python):


from math import pi
r = int(input())
print(2 * pi * r)

Solution (Python):
import math

r = int(input())

print(2*math.pi*r)

Solution (Python):
from math import pi
R = int(input())
print(2*pi*R)

Solution (Python):
R=int(input())
print(R*2*3.14159265358979)

Solution (Python):
import math
r = int(input())
ans = 2*r*math.pi
print(ans)

Solution (Python):
r = int(input())
print(2*r*3.14)

Solution (Python):
r=int(input())
print(2*r*3.14159265358979)

Solution (Python):
R = int(input())
pi = 3.141592
print(2*R*pi)

Solution (Python):
pi = 3.14159265358979
r = int(input())

print(r*2*pi)

Solution (Python):
from math import pi
print(pi*2*int(input()))

Solution (Python):
import math
R = int(input())
print(2*R*math.pi)

Solution (Python):
import math
R=int(input())
print(2*R*math.pi)

Solution (Python):
import math
r = int(input())
print(math.pi*2*r)

Solution (Python):
r = int(input())
s = float()
s = r*3.1415926535*2
print(s)

Solution (Python):
import math
x = int(input())
print((2*x*math.pi))

Solution (Python):
import math
print(2*math.pi*int(input()))

Solution (Python):
import sys
from collections import deque
sys.setrecursionlimit(10**6)
def S(): return sys.stdin.readline().rstrip()
def SL(): return map(str,sys.stdin.readline().rstrip().split())
def I(): return int(sys.stdin.readline().rstrip())
def IL(): return map(int,sys.stdin.readline().rstrip().split())

from math import pi
def Main():
    r = I()
    print(2*pi*r)
    return

if __name__=='__main__':
    Main()

Solution (Python):
import math
x = int(input())
print((2*x*math.pi))

Solution (Python):
print(int(input())*6.283)

Solution (Python):
import math
r = int(input())
radius = 2 * math.pi * r
print(radius)

Solution (Python):
import math
n=int(input())
res=2*math.pi*n
print(res)

Solution (Python):
import math
print(math.pi * int(input()) *2)

Solution (Python):
import math
R = int(input())
print(2*R*math.pi)

Solution (Python):
import math

R = int(input())
print(2 * math.pi * R)

Solution (Python):
import math

R = int(input())
print(2 * math.pi * R)

Solution (Python):
import math
def main():
    r = int(input())
    print(2*math.pi*r)


if __name__ == "__main__":
    main()

Solution (Python):
import math

R = int(input())

print(2*math.pi*R)

Solution (Python):
import math
print(2*math.pi*int(input()))

Solution (Python):
import math
r=int(input())
print(2*r*math.pi)

Solution (Python):
import math
r = int(input())
ans = 2*r*math.pi
print(ans)

Solution (Python):
import math
R=int(input())
print(2*math.pi*R)

Solution (Python):
R = int(input())
print(2*R*3.1415926535)

Solution (Python):
import math
R=int(input())
print(R*2*math.pi)

Solution (Python):
R = int(input())
print(2*3.1415492*R)

Solution (Python):
def main():
    import math

    long = int(input())
    ans = math.pi * 2 * long

    print(ans) 

    

main()

Solution (Python):
from math import pi
r = int(input())
ans = 2 * pi * r
print(ans)

Solution (Python):
from math import pi
n=int(input())
print(2*n*pi)

Solution (Python):
import math
r = int(input())
l = math.pi * 2 * r
print(l)

Solution (Python):
import math
R = int(input())

print(2*R*math.pi)

Solution (Python):
import math 
R = int(input())
print(R*2*math.pi)

Solution (Python):
R = int(input())
ennsyuu = R * 6.28318530717958623200
print(ennsyuu)

Solution (Python):
import math
print(math.pi * int(input()) * 2)

Solution (Python):
r = int(input())
pi = 6.28318530717958623200/2
ans = 2*pi*r
print(ans)

Solution (Python):
import math
def fact(n):
    ans = 1
    for i in range(2, n+1):
        ans*= i
    return ans
def comb(n, c):
    return fact(n)//(fact(n-c)*c)

r = float(input())
print("%.20f"%(2.0*math.pi*r))

Solution (Python):
from math import pi
r=int(input())
print(2*pi*r)

Solution (Python):
import math
r = int(input())

print(2*math.pi*r)

Solution (Python):
import math
PI = math.pi
R = int(input())
print(2*R*PI)

Solution (Python):
import numpy as np
R=int(input())
print(np.pi*2*R)

Solution (Python):
r = int(input())
print(r * 6.28)

Solution (Python):
import math
R = int(input())
print(2 * R * math.pi)

Solution (Python):
"""
~~ Author : Bhaskar
~~ Dated : 13~06~2020
"""

import sys
from bisect import *
from math import floor, sqrt, ceil, factorial as F, gcd, pi
from itertools import chain, combinations, permutations, accumulate
from collections import Counter, defaultdict, OrderedDict, deque

INT_MAX = sys.maxsize
INT_MIN = -(sys.maxsize) - 1
mod = 1000000007
ch = "abcdefghijklmnopqrstuvwxyz"
lcm = lambda a, b: (a * b) // gcd(a, b)
setbit = lambda x: bin(x)[2:].count("1")
INT = lambda type: type(sys.stdin.readline()) if type in [int, float] else type(sys.stdin.readline()).replace("\n", "")
ARRAY = lambda type: list(map(type, sys.stdin.readline().split()))
NUMS = lambda type: map(type, sys.stdin.readline().split())


def solve():

    n = INT(int)
    print(2*pi*n)



if __name__ == "__main__":
    
    
    
    
    solve()

Solution (Python):
import math
r = int(input())
print(2 * r * math.pi)

Solution (Python):
import math

r = int(input())
print(2 * r * math.pi)

Solution (Python):
import math
r = int(input())
print(2*r*math.pi)

Solution (Python):
import math
print(int(input()) * 2 * math.pi)

Solution (Python):
r = int(input())

circle = 2 * r * 3.1415

print(circle)

Solution (Python):
r=int(input())

ans=2*r*3.141592

print(ans)

Solution (Python):
import math
r = int(input())
print(2 * math.pi * r)

Solution (Python):

n = float(input())
print(n*6.283185307179586232)

Solution (Python):
import math
R=float(input())
print((R+R)*math.pi)

Solution (Python):


x=int(input())
p=2*3.1416*x
print(p)

Solution (Python):
r=int(input())
c=2*3.1416*r
print(c)

Solution (Python):
print(int(input())*44/7)

Solution (Python):
import math

r = int(input())
res = 2 * r * math.pi
print(round(res, 2))

Solution (Python):
import math
r=int(input())
print (r*math.pi*2)

Solution (Python):
r = int(input())
print(r*2*3.14)

Solution (Python):

import sys

import fractions
import copy
import bisect
import math
import numpy as np
import itertools
from itertools import combinations_with_replacement


from operator import itemgetter
from sys import stdin

from operator import mul
from functools import reduce
from collections import Counter





j=0
k=0
n=3
r=1
a=[0]






"1行1つの整数を入力を取得し、整数と取得する"




"12 21 332 とか入力する時に使う"
"1行に複数の整数の入力を取得し、整数として扱う"

'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

for i in number_list:
    print(number_list[i-1])

'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

'''
x=[]
y=[]
for i in range(N):
    x1, y1=[int(i) for i in input().split()]
    x.append(x1)
    y.append(y1)
print(x)
print(y)
"複数行に2数値を入力する形式 x座標とy座標を入力するイメージ"
'''

'''
mixlist=[]
for i in range(N):
    a,b=input().split()
    mixlist.append((int(a),b))
print(mixlist)
"複数行にintとstrを複合して入力するやつ，今回はリスト一つで処理している"
'''

'''



"正方行列にstr型の値を入力"
'''




'''
入力
1 2
4 5
7 8
出力結果
[[1, 2], [4, 5], [7, 8]]
'''
"列数に関して自由度の高いint型の値を入力するタイプの行列"


'''
table = [[int(i) for i in input().split()] for m in range(m)]

print(type(N))
print(N)
print(type(M))
print(M)

print(type(table))
print(table)
'''











'''
入力
1234
出力
1
[[1, 2, 3, 4]]
'''




'''
word_list= input().split(" ")
print(word_list[0])
"連続文字列の入力"
"qw er ty とかの入力に使う"
"入力すると空白で区切ったところでlistの番号が与えられる"
'''



'''
A, B, C=stdin.readline().rstrip().split()
print(A)
"リストではなく独立したstr型を入れるなら以下のやり方でOK"
'''




"aという変数に入っているものを大文字にして出力"

















'''
コンビネーションの組み合わせの中身を出力する形式
for i in itertools.combinations(brray, 2)
combinationsをpermutationsにすれば順列になる
今回なら(abc133B)
入力
1 2
5 5
-2 8
出力
[[1, 2], [5, 5], [-2, 8]]
もちろん一次元リストでも使えるし
何よりiもリストのように使えるので便利
'''


'''
def cmb(n,r):
    
    r= min(n-r,r)
    
    if r == 0: return 1
    over = reduce(mul, range(n, n-r, -1))
    
    
    

    under = reduce(mul, range(1, r+1))
    
    
    
    

    return over // under
    
    
    
    
a = cmb(n, r)

'''

'''
import itertools
from itertools import combinations_with_replacement

combinationについて
以下の違いを意識しよう
combinations() p, r 長さrのタプル列、ソートされた順で重複なし

combinations_with_replacement() p, r 長さrのタプル列、ソートされた順で重複あり


使用例 　　　　　　　　　　　                  出力　　
combinations('ABCD', 2)　　　　　　　　　　　　AB AC AD BC BD CD
combinations_with_replacement('ABCD', 2)　　 AA AB AC AD BB BC BD CC CD DD
'''



'''




for i in a.most_common(n):print(i)





 


'''









'''
bisect.bisect_left(a, x, lo=0, h=len(a))
引数
a: ソート済みリスト
x: 挿入したい値
lo: 探索範囲の下限
hi: 探索範囲の上限
(lo, hiはスライスと同様の指定方法)
bisect_leftはソートされたリストaに対して順序を保ったままxを挿入できる箇所を探索します。leftが示す通り、aにすでにxが存在している場合は、挿入箇所は既存のxよりも左側になります。また、lo, hiを指定することで探索範囲を絞り込むことも可能です。デフォルトはaの全体が探索対象です。
'''

'''
素数の判定
'''
def is_prime(n):
    if n == 1: return False

    for k in range(2, int(np.sqrt(n)) + 1):
        
        if n % k == 0:
            return False
            
    return True


'''
npのmaxとmaximumの違い
xs = np.array([1, -2, 3])
np.max(xs, 0)
この出力は3となります．[1, -2, 3]と0の4つの数字のうち，最も大きい値を出力します．

一方で，[max(1, 0), max(-2, 0), max(3, 0)]を出力したい時があります．
その時は，numpyのmaximum関数を用います．

xs = np.array([1, -2, 3])
np.maximum(xs, 0)  

'''

def factorial(x, mod=10**9+7):
    
    
    
    tmp = 1
    for i in range(1, x+1):
        tmp = (tmp * i) % mod
    return tmp
    '''
    Basically, when you do a**d % n, you actually have to calculate a**d, which could be quite large.
    But there are ways of computing a**d % n without having to compute a**d itself, and that is what pow does.
    '''
"
def gcd(a, b):
    while b:
        
        
        a, b = b, a % b
    return a

"
def lcm(a, b):
    return a * b // gcd (a, b)

"
def divisor(n):
    i = 1
    table = []
    while i * i <= n:
        if n%i == 0:
            table.append(i)
            table.append(n//i)
        i += 1
    table = list(set(table))
    return table











'''
ascii_letters = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'
ascii_lowercase = 'abcdefghijklmnopqrstuvwxyz'
ascii_uppercase = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
digits = '0123456789'
hexdigits = '0123456789abcdefABCDEF'
letters = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuv...\xaf\xb0...
lowercase = 'abcdefghijklmnopqrstuvwxyz'
octdigits = '01234567'
printable = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTU...
punctuation = '!"
uppercase = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
whitespace = '\t\n\x0b\x0c\r '
'''
'''
引数endに任意の文字列を指定すると、その文字列が改行の代わりに最後に挿入される。例えば連続するprint()の出力を改行なしで単純に連結したい場合は空文字列''を指定すればよい。

print('abc', end='---')
print('xyz')


print('abc', end='')
print('xyz')

source: print_basic.py
なお、デフォルトで改行されるのは引数endのデフォルト値が改行文字'\n'に設定されているから。
'''

def main():
    n=3
    steps=0
    state=0
    w=1
    j=0
    k=0
    r=float(input())
    print(2*float(r)*3.1415)
    
    
    
    
    
    
    
    
    
    
    


    
    
     

    l = ['aaa', 'bbb', 'ccc']
    x=l.index('aaa')
    
    
    
    

    
        
    
    

    
    
    
    
    DP = np.zeros(w+1, dtype=int)
    exdp=np.zeros((3,4)) 
    
    
    
        
        
    
    
        
        
    


    
    



    '''
    入力
    1234
    出力
    [1, 2, 3, 4]
    '''
    pin_l=["x" for i in range(10)]
    

    ls = ["a", "b", "c", "d", "e"]


    
    

    
    

    
    
    
    
    
    '''
    lsというリストの場合に、1つ飛びの値を取得したい場合には
    ls[::2]
    のようにします。こうすると、
    ["a", "c", "d"]と出力される
    '''

if __name__ == "__main__":
    main()

Solution (Python):
r = int(input())
print(r*6.3)

Solution (Python):
print(int(input()) * 6.3)

Solution (Python):
r = int(input()) * 6.3
print(r)

Solution (Python):
r = int(input())
print(6.3*r)

Solution (Python):
import math
r=int(input())
ans=2*r*math.pi
print(ans)

Solution (Python):
import math
r = int(input())
L = 2 * r * math.pi

print(L)

Solution (Python):
r = int(input())
p = 3.14159265359

print(r*2*p)

Solution (Python):
import math

r = int(input())

print(2 * math.pi * r)

Solution (Python):
import math

r = int(input())

print(2 * math.pi * r)

Solution (Python):
import math
R = int(input())
print(2 * R * math.pi)

Solution (Python):
r = int(input())
print(2*3.14*r)

Solution (Python):
r = int(input())

import math

print(2 * r * math.pi)

Solution (Python):
import math

x = math.pi
r = float(input())
ans = r*2*x
print(ans)

Solution (Python):

R = int(input())
print(2*R*3.141592)

Solution (Python):
r=int(input())
pi=3.141592
print(2*r*pi)

Solution (Python):
import math


def main():
    R = int(input())
    p = math.pi
    print(R*p*2)


if __name__=="__main__":
    main()

Solution (Python):
import numpy as np
r = int(input())
print(2*r*np.pi)

Solution (Python):
R=int(input())
P=3.1415926535
answer=2*R*P
print(answer)

Solution (Python):
import math
P=math.pi
R=int(input())
print(2*math.pi*R)

Solution (Python):
r = int(input())
import math
print(2*math.pi*r)

Solution (Python):
import math
def solve():
    R = int(input())
    print(R*2*math.pi)

if __name__ == '__main__':
    solve()

Solution (Python):
from math import pi
R = int(input())

ans = float(2 * pi * R)

print(ans)

Solution (Python):
r = int(input())

circle = 2 * r * 3.14
print(circle)

Solution (Python):
import math
r = int(input())
print(r*2*math.pi)

Solution (Python):
r=int(input())
print(2 * r * 3.1415)

Solution (Python):
r = int(input())
pi = 3.1415
print(2*pi*r)

Solution (Python):
r=int(input())

print(3.141592653589793*r*2)

Solution (Python):
import numpy as np
R = int(input())
Cir = 2*np.pi*R
print(Cir)

Solution (Python):
import sys
import math
input = lambda: sys.stdin.readline().rstrip()

def main():
    r = int(input())
    print(2*math.pi*r)

if __name__ == '__main__':
    main()

Solution (Python):
R = int(input())

print(R*6.28)

Solution (Python):
import math
R=int(input())
print(2*R*math.pi)

Solution (Python):
R=int(input())
print(2*R*3.1419)

Solution (Python):
import math
a = int(input())
print(math.pi*2*a)

Solution (Python):
import math

r = input()

print(2 * math.pi * int(r))

Solution (Python):
import math
r = int(input())
print(2 * math.pi * r)

Solution (Python):
R = int(input())
print(R*2*3.14159265358979)

Solution (Python):
R=int(input())

print(2*3.14159265*R)

Solution (Python):
import math
print(2*int(input())*math.pi)

Solution (Python):
import math
x = math.pi
r=int(input())
print(2*r*x)

Solution (Python):
r = int(input())

pai = 3.1415
print(2*r*pai)

Solution (Python):
import math
a=math.pi
r=int(input())
print(2*r*a)

Solution (Python):

R = int(input())

print(2 * 3.14 * R)

Solution (Python):
import math
n=int(input())
print(2*n*math.pi)

Solution (Python):
R = int(input())
print(R*6.283)

Solution (Python):
import math

R=float(input())
print(2.0*R*math.pi)

Solution (Python):
import math
r=int(input())
x=2*r*314159265358979
print(x/100000000000000)

Solution (Python):
print(int(input())*6.28318530717958623200)

Solution (Python):
import math as m
print(int(input())*2*m.pi)

Solution (Python):
n = input()
pi = 3.142592
R = 2 * pi * int(n)
print(R)

Solution (Python):
from math import pi

r = int(input())
print(pi * r * 2)

Solution (Python):
import math
R = int(input())
print(2 * math.pi * R)

Solution (Python):
import math
r = int(input())

ans = 2 * math.pi * r
print(ans)

Solution (Python):
R = int(input())
print(2*3.141592*R)

Solution (Python):
import math

n = int(input())

kekka = 2 * n * math.pi
print(kekka)

Solution (Python):
import math
r = float(input())

print(math.pi * 2*r)

Solution (Python):
import math
R = int(input())
print(R * 2 * math.pi)

Solution (Python):
x=float(input())
p=2*3.14*x
A="dlfnsdfjsdjfsdfjsdfnksdkjnfjksndfkjnskjfkjsdkjfnskjdfknsdkjfskdnfkjsdn"
print(p)

Solution (Python):
import math
def main():
    n = int(input())
    r = 2 * math.pi * n
    print(round(r,2))




main()

Solution (Python):

R = int(input())
print(2*3.14159265359*R)

Solution (Python):
import math
r = int(input())
print(2*r*math.pi)

Solution (Python):
import math
print(2*int(input())*math.pi)

Solution (Python):
import math
R = int(input())
print(2*(math.pi)*R)

Solution (Python):
import math
s = int(input())
print(2*math.pi*s)

Solution (Python):
import math

radious = int(input())

ensyu = 2 * radious * math.pi
print(ensyu)

Solution (Python):
import numpy as np
R = int(input())
print(2*np.pi*R)

Solution (Python):
import math
math.pi

r = (float)(input())
ret = 2.0 * r * math.pi
print("{}".format(ret))

Solution (Python):
import math
A = int(input())
a = A * 2 * math.pi
print(a)

Solution (Python):

import math

r = input().rstrip()
r = int(r)


x = math.pi

ans = (2 * r) * x
print(ans)

Solution (Python):
import math
print(math.pi*2*int(input()))

Solution (Python):
import math
print(int(input())*2*math.pi)

Solution (Python):
R=input()

R=float(R)

print(R*2*3.14)

Solution (Python):
import numpy as np
pi = np.pi
a = int(input())
print(2 * a * pi)

Solution (Python):
import math
r = int(input())
print(2*math.pi*r)

Solution (Python):
r = int(input())
import math
pi = math.pi
l = 2 * pi * r
print(l)

Solution (Python):
import math as ma
r=int(input())
print(2*r*ma.pi)

Solution (Python):
import math

r = int(input())
print(r*2*math.pi)

Solution (Python):
print(int(input()) * 3.142 * 2)

Solution (Python):
import math
r = float(input())
print(2*r*math.pi)

Solution (Python):
import math

R=int(input())

print(2*math.pi*R)

Solution (Python):
import math

R=int(input())

print(R*2*math.pi)

Solution (Python):
import math
print(int(input()) * 2 * math.pi)

Solution (Python):
r = int(input())
print(r*2*3.141592)

Solution (Python):
print(int(input())*6.28)

Solution (Python):

print(int(input()) * 2 * 3.14159265)

Solution (Python):
import math


r = int(input())

print(2 * math.pi * r)

Solution (Python):
import math
R = int(input())
print(2 * math.pi * R)

Solution (Python):
import math
a=int(input())
print(2*math.pi*a)

Solution (Python):
import math

def main():
  R = input()
  answer = float(R) * 2 * math.pi  
  print(answer)
  
if __name__ == '__main__':
  main()

Solution (Python):

import math
R = int(input())

print(2 * math.pi * R)

Solution (Python):
import math
r = float(input())
print(2*math.pi*r)

Solution (Python):
import math
r=int(input())
print(2*r*math.pi)

Solution (Python):
import math

r = int(input())
print(2 * r * math.pi)

Solution (Python):
import math
R = int(input())
ans = 2*R*math.pi
print(ans)

Solution (Python):
import math
r = int(input())
print(2 * r * math.pi)

Solution (Python):
import math
r = int(input())

print(2*r*math.pi)

Solution (Python):
pi = 3.141592
r = int(input())
print(2 * r * pi)

Solution (Python):
import math

r = int(input())

print(2*r*math.pi)

Solution (Python):
import math
r=int(input())
print(2*r*math.pi)

Solution (Python):
import math

r = int(input())

print(2*math.pi*r)