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

-----Sample Output-----
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.

Difficulty: introductory

Starter code:

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

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

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

def resolve():
    pi = 3.14159265
    r = int(input())
    print(2*r*pi)
resolve()

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

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

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

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

import math
R = int(input())
ans = 2.0*math.pi*R
print(ans)

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

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

a = int(input())

n = 3.141592


print((a + a) * n)

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


import math

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


def main():
    import math
    n = int(input())
    ans = 2 * math.pi * n
    return ans


def __starting_point():
    print((main()))

__starting_point()

from math import pi
#a = list(map(int, input().rstrip().split()))
n=int(input())
print(n*2*pi)

import numpy

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


import math
p=math.pi
r=int(input())

print(2*r*p)

import math,string,itertools,fractions,heapq,collections,re,array,bisect,sys,random,time, copy,bisect
#from operator import itemgetter
#from heapq import heappush, heappop
#import numpy as np
#from scipy.sparse.csgraph import shortest_path, floyd_warshall, dijkstra, bellman_ford, johnson
#from scipy.sparse import csr_matrix
#from decimal import Decimal, ROUND_HALF_UP, ROUND_HALF_EVEN
import sys

sys.setrecursionlimit(10**7)
inf = 10**20
mod = 10**9 + 7

stdin = sys.stdin

ni = lambda: int(ns())
nf = lambda: float(ns())
na = lambda: list(map(int, stdin.readline().split()))
nb = lambda: list(map(float, stdin.readline().split()))
ns = lambda: stdin.readline().rstrip()  # ignore trailing spaces

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

import math

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

import math
r = int(input())

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


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

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

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

import math
print(int(input())*math.tau)

r = int(input())

print((r * 3.1416 * 2))


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

import numpy as np

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

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

import sys
import math

R = int(input())

print(2 * math.pi * R)

# coding: utf-8
# Your code here!
import math

R = int(input())

print(R*2*math.pi)

#ABC163
R = int(input())
#----------以上入力----------
import math
print(2*R*math.pi)

import math
r = int(input())

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


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

r = float(input())

pi = float('3.1415926535897932384626')
s = 2 * r * pi

print(s)

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

# coding: utf-8
# Your code here!

r = int(input())

ans = r * 2 * 3.14159265359
print(ans)

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

import math

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


import math


def main() -> None:
    r = int(input())

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


def __starting_point():
    main()

__starting_point()

a=int(input())
print(2*3.1416*a)

import numpy as np

R = int(input())

print((2 * np.pi * R))


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

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

#ABC163
R = int(input())
#----------以上入力----------
import numpy as np
print(2*R*np.pi)

import math

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


import numpy as np

R = int(input())

print(R * 2 * np.pi)

r = int(input())
print((2 * r * 3.1415926535))


R = int(input())
print(2 * R * 3.1415926535)

print(2 * float(input()) * 3.14159)

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

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


def N():
    return int(input())
def L():
    return list(map(int,input().split()))
def NL(n):
    return [list(map(int,input().split())) for i in range(n)]
mod = pow(10,9)+7

#import numpy as np
import sys
import math
import collections

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

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

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

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

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

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


import math

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

from decimal import Decimal

r = int(input())
pie = Decimal('3.14159')

print(2 * pie * r)

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


import math

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

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


import numpy as np

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

# 163 A
import math
math.pi

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

import sys
from collections import deque, defaultdict, Counter
from itertools import accumulate, product, permutations, combinations
from operator import itemgetter
from bisect import bisect_left, bisect_right
from heapq import heappop, heappush
from math import ceil, floor, sqrt, gcd, inf, pi
from copy import deepcopy
import numpy as np
import scipy as sp

INF = inf
MOD = 1000000007

r = int(input())

tmp = 0
res = 0

res = 2 * r * pi

print(res)


import math 
r = int(input())

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

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

import math
r = int(input())

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



import math

r = int(input())

r_t = r*2


print(math.pi * r_t)

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

from math import pi

integer = int(input())

print(2 * integer * pi)

import numpy as np
R=int(input())
circle=float(R*2*np.pi)
print(circle)


import math
def __starting_point():

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

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

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

import math
R = int(input())

print(2*math.pi*R)

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

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

import math

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

from math import pi

R = int(input())

print(2*R*pi)

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

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

r = int(input())
print((r * 6.28318530717958623200))


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

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

import math

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

r = int(input())

print((2 * r * 3.1415926535))