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):


"""
Created on Sun Apr 26 13:36:36 2020

@author: hiroki
"""

import math

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

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

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

num = 2*R*math.pi
print(f'{num:.3f}')

Solution (Python):
if __name__ == '__main__':
	R = int(input())
	pi = 3.1415926535
	print(2 * R * pi)

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

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

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

Solution (Python):
import math

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

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

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):
import math
print(int(input()) * 2.0 * math.pi)

Solution (Python):
import math

r=int(input())

cir = 2 * r * math.pi

print(cir)

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

Solution (Python):
from math import pi

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

if __name__ == "__main__":
    main()

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

Solution (Python):

import math
n = int(input())
pi = math.acos(-1)
print(2*pi*n)

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):


r = int(input())
ans = 2 * r * 3.14
print(ans)

Solution (Python):
import math


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


main()

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

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

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

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

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

Solution (Python):
print(int(input())*2*3.145)

Solution (Python):
print(int(input())*2*3.145)

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

print(r*2*3.1415)

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

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

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

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

print(2 * math.pi * R)

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

Solution (Python):
import math

a=int(input())

print(a*2*math.pi)

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

print(2 * R * 3.14)

Solution (Python):
from math import pi

r = int(input())

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

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

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):
n = int(input())
print(2*3.1415*n)

Solution (Python):
import math

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

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

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

print(2*n*pi)

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

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

Solution (Python):
import numpy as np

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

Solution (Python):
import math

radius = int(input())
length = 2*math.pi*radius
print(length)

Solution (Python):
import math
pi = math.pi

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

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

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

Solution (Python):
import math

r = int(input())

radius = 2 * math.pi * r

print(radius)

Solution (Python):
import math
R=int(input())
def circle_round(radius):
  return 2 * math.pi * radius
if __name__ == '__main__':
  print(circle_round(R))

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

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

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

Solution (Python):
import math

r = int(input())
all = r*2
result = all * math.pi

print(result)

Solution (Python):
import math
def count():
    R=int(input())
    x=math.pi
    print(2*x*R)
if  __name__=='__main__':
    count()

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

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

Solution (Python):
from math import pi

r = int(input())
print("%.2f"%(2*pi*r))

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

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

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

Solution (Python):


def main():
    R = int(input())
    print(R * 2 * 3.1415926535323846)

if __name__ == '__main__':
    main()

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

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

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

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

Solution (Python):
import math

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

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

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

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

l=float(math.pi*2*r)

print(round(l,3))

Solution (Python):
import math

r = int(input())

print(2*r*math.pi)

Solution (Python):
import numpy as np

r = int(input())

print(2*np.pi*r)

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

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

print(R*6.283)

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 = input()
RR=float(R)

Ans = 2*RR*math.pi


print(Ans)

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

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

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

Solution (Python):
import math
print math.pi * 2 * float(raw_input())

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

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

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

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

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

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

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

Solution (Python):
from math import pi

print(float(input())*pi*2)

Solution (Python):
print(int(input())*2*3.141)

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

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

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

print(2*R*3.14)

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

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

Solution (Python):
import math
r = int(input())
print(r*8*math.pi/4)

Solution (Python):
import math


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

Solution (Python):
pi = 3.141592653979
r = int(input())
print(2*r*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
a=int(input())
print(math.pi*2*a)

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

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

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

enshu = (a+a)*3.14
print(enshu)

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

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

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

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

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

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

print(2 * a * 3.14)

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

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

Solution (Python):

hankei = int(input())

print(hankei * 2 * 3.14)

Solution (Python):
import math

R = int(input())

print(2 * R * math.pi)

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

Solution (Python):
R = float(input())
print(R*6.2831)

Solution (Python):
R=int(input())
print(R*2*3.141592653)

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

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

Solution (Python):
import sys
import math
from collections import deque
from decimal import Decimal, ROUND_HALF_UP, ROUND_HALF_EVEN
def I(): return int(sys.stdin.readline())
def MI(): return map(int, sys.stdin.readline().split())
def LI(): return list(map(int, sys.stdin.readline().split()))
def LI2(N): return [list(map(int, sys.stdin.readline().split())) for i in range(N)]
def S(): return sys.stdin.readline()
def LS(): return sys.stdin.readline().split()
def LS2(N): return [sys.stdin.readline().split() for i in range(N)]
def FILL(i,h,w): return [[i for j in range(w)] for k in range(h)]
def sisha(num,digit): return Decimal(str(num)).quantize(Decimal(digit),rounding=ROUND_HALF_UP)

MOD = 1000000007
INF = float("inf")
sys.setrecursionlimit(10**6+10)
input = sys.stdin.readline

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

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

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

Solution (Python):
import math

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

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

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

Solution (Python):
import math

r = int(input())

print(2*math.pi*r)

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

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

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

Solution (Python):
from math import pi
n = int(input())
print('%.18f'%(2.0 * pi * n))

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

Solution (Python):
def main():
  R=int(input())
  print(2*3.1416*R)
if __name__=='__main__':
  main()

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

Solution (Python):
import math

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

Solution (Python):

R = int(input())
ens = 6.28 * R
print(ens)

Solution (Python):



import numpy
import math

x = int(input())

print(2*x*math.pi)

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

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

print(2*3.14*R)

Solution (Python):
import math

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

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

Solution (Python):
printn = lambda x: print(x,end='')
inn = lambda : int(input())
inl   = lambda: list(map(int, input().split()))
inm   = lambda:      map(int, input().split())
ins = lambda : input().strip()
DBG = True 
BIG = 10**18
R = 10**9 + 7

def ddprint(x):
  if DBG:
    print(x)

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

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

Solution (Python):
import math

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

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

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

Solution (Python):
import math

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

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

print(2 * 3.14159265 * r)

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

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

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

print(n*2*3.14)

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

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

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

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

Solution (Python):
from math import pi

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

Solution (Python):
import math
print(2.0 * float(input()) * math.pi)

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

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

Solution (Python):
a=input()
print(float(a)*6.28)

Solution (Python):
a=input()
print(float(a)*2*3.141592653589)

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

Solution (Python):

R = int(input())
print(2 * 3.1415 * R)

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

Solution (Python):
round = 6.28318530717958623200

 
r = int(input())
print(r*round)

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

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

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

Solution (Python):
import math

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

Solution (Python):



def main():
	r = int(input())
	
	s = 2*r*3.1415926
	print (s)

if __name__ == '__main__':
	main()

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

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

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

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

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

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

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

Solution (Python):
import math

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

Solution (Python):
import math

def resolve():
    n = int(input())
    ans = math.pi*n*2
    print(ans)
resolve()

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

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

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

Solution (Python):
import numpy as np
print(int(input())*6.28)

Solution (Python):
import math

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

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

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

Solution (Python):
N=int(input())
x=2*N*3.1415926535897
print(x)

Solution (Python):
import math

r = int(input())

al = math.pi * r *2

print(al)

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

print(2*R*math.pi)

Solution (Python):
line = input()

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

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

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

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

Solution (Python):
r=int(input())
print(r*6.282)

Solution (Python):
import math

R = int(input())

print(R*2*math.pi)

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

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

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

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

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

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

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

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

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

print(R*math.pi*2)

Solution (Python):
pi=3.14
r=float(input())
ans=pi*2*r
print(float(ans))

Solution (Python):

pi = 3.141592653589793238
a=int(input())
print(pi * 2 * a)

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

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):
import math

if __name__ == "__main__":
    R = int(input())
    print(2*math.pi*R)

Solution (Python):
R = input()
R = int(R)
print(2*R*3.14159265358979323846264338327950288)

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

Solution (Python):
R = int(input())
print(2 * R * 3.14151592)

Solution (Python):
import math

r = int(input())

ans = r * 2 * math.pi

print(ans)

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

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

Solution (Python):
import math

R = int(input())

ans = 2*math.pi*R

print(ans)

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

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

import math

print(2*r*math.pi)

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

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

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

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

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

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

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

Solution (Python):
from math import pi

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

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

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

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

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

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

Solution (Python):
import math

r = float(input())

print(math.pi * r * 2 )

Solution (Python):
from math import *
from copy import *
from string import *				
from random import *
from sys import stdin
from sys import maxsize
from operator import *				
from itertools import *
from collections import Counter		
import math

def bin1(l,r,k,t,b,val,ans):
	if(l>r):
		return ans
	else:
		mid=(l+r)//2
		v=k**mid
		if(v==val):
			return v
		elif(v>val):
			ans=mid
			return bin1(mid+1,r,k,t,b,val,ans)
		else:
			return bin1(l,mid-1,k,t,b,val,ans)
		
def bin2(l,r,k,t,b,val,ans):
	if(l>r):
		return ans
	else:
		mid=(l+r)//2
		v=t*(k**mid)+b*(mid)
		if(v==val):
			return v
		elif(v>val):
			ans=mid
			return bin2(l,mid-1,k,t,b,val,ans)
		else:
			return bin2(mid+1,r,k,t,b,val,ans)

def SieveOfEratosthenes(n): 
      
    
    
    
    prime = [True for i in range(n+1)] 
    p = 2
    while (p * p <= n): 
          
        
        if (prime[p] == True): 
              
            
            for i in range(p * p, n+1, p): 
                prime[i] = False
        p += 1
    return prime
def bin(l,r,ll,val):
	if(l>r):
		return -1
	else:
		mid=(l+r)//2
		if(val>=ll[mid][0] and val<=ll[mid][1]):
			return mid
		elif(val<ll[mid][0]):
			return bin(l,mid-1,ll,val)
		else:
			return bin(mid+1,r,ll,val)
def deci(n):
	s=""
	while(n!=0):
		if(n%2==0):
			n=n//2
			s="0"+s
		else:
			n=n//2
			s="1"+s
	return s
def diff(s1,s2):
	if(len(s1)<len(s2)):
		v=len(s1)
		while(v!=len(s2)):
			s1="0"+s1
			v=v+1
	else:
		v=len(s2)
		while(v!=len(s1)):
			s2="0"+s2
			v=v+1
	c=0
	for i in range(len(s1)):
		if(s1[i:i+1]!=s2[i:i+1]):
			c=c+1
	return c
from sys import stdin, stdout 
if __name__ == '__main__':
	n=int(stdin.readline())
	stdout.write(str(2*pi*n)+"\n")

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

Solution (Python):
print(int(input().strip()) * 2 * 3.141592653)

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

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

Solution (Python):
import math

r = int(input())

print( 2 * r * math.pi)

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

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

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

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

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

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

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

Solution (Python):
a=eval(input())
print("{:.10}".format(a*2*3.141592653))

Solution (Python):
import math

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

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

Solution (Python):
import math

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

Solution (Python):
r=int(input())
print(2*3.1415926*r)

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

print(2 * R * 3.141592 )

Solution (Python):
n=int(input())
import math
ans=2*math.pi*n
print('{:.3f}'.format(ans))

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

Solution (Python):
import math
a='Source code should be longer than 50 characters -_-'
print(2*math.acos(-1)*int(input()))

Solution (Python):
import math

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

Solution (Python):
pi = 3.141592653589793
r = float(input())
ans = pi*r*2
print(ans)

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

Solution (Python):
n = int(input())
p=3.142

print(2*n*p)

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

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

Solution (Python):
import math

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

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

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

Solution (Python):
import math

r = int(input())

r = r*2*math.pi

print(r)

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

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

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

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

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

Solution (Python):
import math

def circle_cul(r):
  return 2*math.pi*r

r=int(input())
print(circle_cul(r))

Solution (Python):
import math

R = int(input())
print('{:.9f}'.format(2*math.pi*R))

Solution (Python):
import sys
import math



def II(): return int(sys.stdin.readline())
def MI(): return map(int, sys.stdin.readline().split())
def MI1(): return map(int1, sys.stdin.readline().split())

def LI(): return list(map(int, sys.stdin.readline().split()))

def LLI(rows_number): return [LI() for _ in range(rows_number)]
def SR(): return sys.stdin.readline().rstrip()

ascii_lowercase = 'abcdefghijklmnopqrstuvwxyz'
ascii_uppercase = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
ascii_uppercase2 = 'ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ'


p2D = lambda x: print(*x, sep="\n")
p2E = lambda x: print(''.join(x))
p2S = lambda x: print(*x, sep=" ")



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

Solution (Python):
from math import pi

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

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

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

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

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

Solution (Python):
import math

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


resolve()

Solution (Python):
from math import pi

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

Solution (Python):

"""
Spyderエディタ

これは一時的なスクリプトファイルです
"""

import math

n = int(input())

print(2 * math.pi * n)

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

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

Solution (Python):
import numpy as np

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

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

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

Solution (Python):
import math

R = int(input())

print(str(2 *R * math.pi))

Solution (Python):
import math

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

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

Solution (Python):
import math

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

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

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

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

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

Solution (Python):
from math import acos
a=int(input())
k=2*a*2*acos(0.0)
print(k)

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

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

Solution (Python):
print(3.1415926535897932384626433834* 2* (int(input())))

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())
ans = math.pi * R * 2

print(ans)

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

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

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

Solution (Python):
import math

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

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

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

print(2*R*math.pi)

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

Solution (Python):
import math

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

Solution (Python):
print(3.1415926535897932384626433834*2*int(input()))

Solution (Python):
print(3.1415926535897932384626433834*2*int(input()))

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

print(2*r*math.pi)

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

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

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

print(2*r*3.14159)

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

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

Solution (Python):
from math import pi

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

if __name__ == '__main__':
    main()

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

Solution (Python):
import math

r = int(input())

print(r * 2 * math.pi)

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

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

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

Solution (Python):

import math


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


if __name__ == "__main__":
    main()

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

answer = role * 2 * 3.14159265358979

print(answer)

Solution (Python):
import math
r = int(input())
x = r * math.pi * 2
n = 10
y = math.floor(x * 10 ** n) / (10 ** n)
print(y)

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 sys
import os
import math
import string

ii = lambda: int(sys.stdin.buffer.readline().rstrip())
il = lambda: list(map(int, sys.stdin.buffer.readline().split()))
fl = lambda: list(map(float, sys.stdin.buffer.readline().split()))
iln = lambda n: [int(sys.stdin.buffer.readline().rstrip()) for _ in range(n)]

iss = lambda: sys.stdin.buffer.readline().decode().rstrip()
sl = lambda: list(map(str, sys.stdin.buffer.readline().decode().split()))
isn = lambda n: [sys.stdin.buffer.readline().decode().rstrip() for _ in range(n)]

lcm = lambda x, y: x * y / math.gcd(x, y)

MOD = 10 ** 9 + 7


def main():
    if os.getenv("LOCAL"):
        sys.stdin = open("input.txt", "r")

    N = ii()
    print(2*N*3.14)


if __name__ == '__main__':
    main()

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

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

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

Solution (Python):
R = float(input())
print(R*6.28)

Solution (Python):
import math

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

if __name__ == "__main__":
    main()

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

Solution (Python):
from math import pi


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


if __name__ == "__main__":
    main()

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

Solution (Python):
from math import pi

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

Solution (Python):
import numpy as np

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

Solution (Python):
import math

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

Solution (Python):
import numpy as np

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

Solution (Python):
import math

def Main():
    n = int(input()) * 2
    
    print( n * math.pi )

if __name__ == "__main__":
    Main()

Solution (Python):
import math
def main():
    R = int(input())
    print(2*math.pi*R)
if __name__ == "__main__":
    main()

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

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

Solution (Python):
print(2*3.1415926*int(input()))

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

Solution (Python):
import math

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

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

Solution (Python):
import sys
from collections import *
import heapq
import math
from math import gcd
import bisect
import copy
from itertools import permutations,accumulate,combinations,product
def input():
    return sys.stdin.readline()[:-1]
def ruiseki(lst):
    return [0]+list(accumulate(lst))
mod=pow(10,9)+7
al=[chr(ord('a') + i) for i in range(26)]
direction=[[1,0],[0,1],[-1,0],[0,-1]]

n=int(input())
m=math.pi
print(2*n*m)

Solution (Python):
validation=False
Answer=()


while validation == False:
      R=float(input(""))
      if R>=1 and R<=100:
            validation = True
      else:
            break
      

Answer=((R*2)*3.14159)

print(Answer)

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 numpy as np
import sys
read = sys.stdin.read
readline = sys.stdin.readline
readlines = sys.stdin.readlines
p = np.pi
R = int(input())

print(2*R*p)

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

print(R*2*math.pi)

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

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

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

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

Solution (Python):
R = int(input())
print(4 * 3.14 * R / 2)

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

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

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

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

print(2*R*3.14)

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

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 as m
r=int(input())
print(2*m.pi*r)

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