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 math

r = int(input())

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

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

import math

print(2 * R * math.pi)

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

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

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

if __name__ == "__main__":
    main()

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

Solution (Python):
from math import pi

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

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

print(r*2*3.1415)

Solution (Python):
import math


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


if __name__ == '__main__':
    resolve()

Solution (Python):
import math

r = int(input())


print(2*r*math.pi)

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

Solution (Python):
import math
import copy
import sys
import fractions


import decimal
import heapq
import collections
import itertools
import bisect



sys.setrecursionlimit(100001)







def getInputIntList():
    outputDataList = []
    inputData = input().split()
    outputDataList = [int(n) for n in inputData]

    return outputDataList


def getSomeInputInt(n):
    outputDataList = []
    for i in range(n):
        inputData = int(input())
        outputDataList.append(inputData)

    return outputDataList


def getSomeInputListInt(n):
    inputDataList = []
    outputDataList = []
    for i in range(n):
        inputData = input().split()
        inputDataList = [int(n) for n in inputData]
        outputDataList.append(inputDataList)

    return outputDataList




r = float(input())

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

Solution (Python):
n = int(input())
x = n * 2 * 3.1459265
print(x)

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

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

Solution (Python):
import math

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

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

Solution (Python):
from math import pi

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

Solution (Python):
import math

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

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

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


if __name__ == '__main__':
    main()

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

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

Solution (Python):
import math
import sys

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

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

Solution (Python):
import sys
import math

input = sys.stdin.readline


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


if __name__ == "__main__":
    main()

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

Solution (Python):
import math
from functools import reduce
from collections import deque
import sys
sys.setrecursionlimit(10**7)


def get_nums_l():
    return [ int(s) for s in input().split(" ")]


def get_nums_n(n):
    return [ int(input()) for _ in range(n)]


def get_all_int():
    return map(int, open(0).read().split())

def log(*args):
    print("DEBUG:", *args, file=sys.stderr)

r = int(input())
print(2 * r * 3.141519)

Solution (Python):
import sys
from math import sqrt, pi
from collections import Counter, defaultdict, deque

input = sys.stdin.readline
sys.setrecursionlimit(10 ** 6)


def I():
    return int(input())


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


def LI():
    return list(MI())


def LIN(n: int):
    return [I() for _ in range(n)]


inf = float("inf")
mod = 10 ** 9 + 7


def main():
    r = I()
    print(2 * r * pi)
    pass


if __name__ == "__main__":
    main()

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

print(math.pi * r *2)

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

Solution (Python):
from math import pi

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

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

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

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

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

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):
from math import pi

r = int(input())

print(2 * pi * r)

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

p = math.pi

print(2 * n * p)

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

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

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

Solution (Python):
import sys
import numpy as np
import math
input=sys.stdin.readline

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

r=int(input())


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

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

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

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

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

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 sys
def input(): return sys.stdin.readline().rstrip()
import numpy as np
def main():
    r=int(input())
    print(2*np.pi*r)

if __name__=='__main__':
    main()

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())

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

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

import math

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


if __name__ == '__main__':
    main()

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

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

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

c = 2 * 3.1415926 * r

print(c)

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

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

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

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

result = 3.1415926535*2*R
print(result)

Solution (Python):
import math

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

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

import math

print(math.pi*R*2)

Solution (Python):
import math

R = int(input())

print(2*R*math.pi)

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

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

Solution (Python):
import numpy as np

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

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

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

pai=3.14159265358979

print(r*2*pai)

Solution (Python):
pi = 3.1415926


def inp():
    return(int(input().rstrip()))
def inlt():
    return(list(map(int,input().rstrip().split())))
def insr():
    s = input().rstrip()
    return(s[:len(s) - 1])
def invr():
    return(map(int,input().rstrip().split()))

n = inp()
print(2*n*pi)

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

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

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

import math

print(2*r*math.pi)

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

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

Solution (Python):
import sys
sys.setrecursionlimit(10**6)
from math import floor,ceil,sqrt,factorial,log,pi
from heapq import heappop, heappush, heappushpop
from collections import Counter,defaultdict,deque
from itertools import accumulate,permutations,combinations,product,combinations_with_replacement
from bisect import bisect_left,bisect_right
from copy import deepcopy
from operator import itemgetter
from fractions import gcd
mod = 10 ** 9 + 7
inf = float('inf')
ninf = -float('inf')
 

def ii(): return int(sys.stdin.readline().rstrip()) 
def mii(): return map(int,sys.stdin.readline().rstrip().split())
def limii(): return list(mii()) 
def lin(n:int): return [ii() for _ in range(n)]
def llint(n: int): return [limii() for _ in range(n)]

def ss(): return sys.stdin.readline().rstrip() 
def mss(): return sys.stdin.readline().rstrip().split()
def limss(): return list(mss()) 
def lst(n:int): return [ss() for _ in range(n)]
def llstr(n: int): return [limss() for _ in range(n)]






n=ii()

print(2*pi*n)

Solution (Python):

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

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

print(2*R*pi)

Solution (Python):
import numpy as np

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

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

Solution (Python):
import math

r = int(input())

print(2 * r * math.pi)

Solution (Python):
import sys
import math
import collections
from collections import deque
from functools import reduce
import heapq
r = int(input())





print(2*r*math.pi)

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

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

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

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):
R = int(input())
import math
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):
import math
r = int(input())
print(math.pi  * r * 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):
r = int(input())
print(r*2*3.14159265358979)

Solution (Python):
def main():
    
    S = float(input())
    
    pi = 3.1415
    
    print(2 * pi * S)
    
main()

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

Solution (Python):
import math

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

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

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

print(2*r*math.pi)

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

print(math.pi * a * 2)

Solution (Python):
import sys
input = sys.stdin.readline
from collections import *
from math import *

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

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

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


main()

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

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

Solution (Python):
import sys
import math
import collections
from collections import deque
from functools import reduce
import heapq
r = int(input())





print(2*r*math.pi)

Solution (Python):
from math import pi

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

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

Solution (Python):
from math import pi

R = int(input())

print(2*R*pi)

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

Solution (Python):

import math
R = int(input())

print(2 * math.pi * R)

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

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

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

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

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

Solution (Python):


import sys
stdin = sys.stdin
import math

def ns(): return stdin.readline().rstrip()
def ni(): return int(ns())
def na(): return list(map(int, stdin.readline().split()))

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

if __name__ == "__main__":
    main()

Solution (Python):
import bisect
import cmath
import heapq
import itertools
import math
import operator
import os
import random
import re
import string
import sys
from collections import Counter, defaultdict, deque
from copy import deepcopy
from decimal import Decimal
from functools import lru_cache, reduce
from math import gcd
from operator import add, itemgetter, mul, xor

import numpy as np

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

sys.setrecursionlimit(10 ** 9)
INF = float("inf")
IINF = 10 ** 18
MOD = 10 ** 9 + 7




r = int(sys.stdin.buffer.readline())
a = r * 2 * math.pi
print(a)

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

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

Solution (Python):
from math import pi

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

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

Solution (Python):
import sys
import math

from collections import defaultdict
from collections import deque
def load(vtype=int):
    return vtype(input().strip())
def load_list(seplator=" ", vtype=int):
    return [vtype(v) for v in input().strip().split(seplator)]
def exit():
    import sys
    sys.exit(0)
def perm_sub(li, used):
    if len(li) == len(used):
        return [deque()]
    k = []
    for i in range(len(li)):
        if i in used:
            continue
        used.add(i)
        sub_list = perm_sub(li, used)
        for sub in sub_list:
            sub.appendleft(li[i])
        k.extend(sub_list)
        used.discard(i)
    return k
def perm_li(li):
    return perm_sub(li, set())
def perm_n(n):
    return perm_sub(list(range(n)), set())
def join_i(li, sep=""):
    return sep.join([str(e) for e in li])
def li2n(li):
    n, base = 0, 1
    for i in range(len(li)-1, -1, -1):
        n += li[i] * base
        base *= 10
    return n
def sli2ili(li):
    return [int(s) for s in li] 
def prime_list(n):
    li = [i for i in range(2, n+1)]
    for i in range(len(li)):
        if li[i] >= int(math.sqrt(n)):
            break
        if li[i] == -1:
            continue
        for j in range(i+1, len(li)):
            if li[j] % li[i] == 0:
                li[j] = -1
    return [n for n in li if n != -1]
def gcd(a, b):
    a, b = max(a, b), min(a, b)
    while True:
        r = a % b
        if r == 0: return b
        a, b = b, r
def lcm(a, b):
    return int(a * b / gcd(a,b))
def all_subset(li):
    s = []
    n = len(li)
    for bit in range(0, (1<<(n+1))):
        ss = set()
        for i in range(0, n):
            if (bit & (1 << i)):
                ss.add(li[i])
        s.append(ss)
    return s
def factorial(n):
    if n == 1:
        return 1
    return n * factorial(n-1)
def mCn(m, n):
    def factorial_ntimes(m, n):
        r = 1
        while n:
            r *= m
            m -= 1
            n -= 1
        return r
    return int(factorial_ntimes(m, n) / factorial(n))

r = load()

print(2 * r * math.pi)

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

print(2*R*pi)

Solution (Python):


import sys
from math import pi

def input(): return sys.stdin.readline().strip()
def list2d(a, b, c): return [[c] * b for i in range(a)]
def list3d(a, b, c, d): return [[[d] * c for j in range(b)] for i in range(a)]
def list4d(a, b, c, d, e): return [[[[e] * d for j in range(c)] for j in range(b)] for i in range(a)]
def ceil(x, y=1): return int(-(-x // y))
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(N=None): return list(MAP()) if N is None else [INT() for i in range(N)]
def Yes(): print('Yes')
def No(): print('No')
def YES(): print('YES')
def NO(): print('NO')
sys.setrecursionlimit(10 ** 9)
INF = 10 ** 18
MOD = 10 ** 9 + 7

R = INT()

ans = R * 2 * pi
print(ans)

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

print(2*n*math.pi)

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

print(2 * r * pi)

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

print(math.pi*2*n)

Solution (Python):

"""
Created on Sun Apr 19 20:41:02 2020

@author: Kanaru Sato
"""
import math

r = int(input())

print(2*r*math.pi)

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

Solution (Python):
import sys

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*R*math.pi)

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

Solution (Python):
import numpy as np
import math

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

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

Solution (Python):
import sys, bisect, math, itertools, string, queue, copy


from collections import Counter,defaultdict,deque
from itertools import permutations, combinations
from heapq import heappop, heappush
from fractions import gcd

sys.setrecursionlimit(10**8)
mod = 10**9+7
def inp(): return int(input())
def inpm(): return map(int,input().split())
def inpl(): return list(map(int, input().split()))
def inpls(): return list(input().split())
def inplm(n): return list(int(input()) for _ in range(n))
def inplL(n): return [list(input()) for _ in range(n)]
def inplT(n): return [tuple(input()) for _ in range(n)]
def inpll(n): return [list(map(int, input().split())) for _ in range(n)]
def inplls(n): return sorted([list(map(int, input().split())) for _ in range(n)])

def main():
    r = inp()
    print(r*2*math.pi)
    
if __name__ == "__main__":
    main()

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

Solution (Python):
N = float(input())
N *= 2 * 3.14159265

print(N)

Solution (Python):

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

Solution (Python):
from collections import Counter,defaultdict,deque
from heapq import heappop,heappush,heapify
import sys,bisect,math,itertools,fractions,pprint
sys.setrecursionlimit(10**8)
mod = 10**9+7
INF = float('inf')
def inp(): return int(sys.stdin.readline())
def inpl(): return list(map(int, sys.stdin.readline().split()))

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

Solution (Python):
import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines
sys.setrecursionlimit(10 ** 7)

from  math import pi

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

Solution (Python):
import math

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

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


if __name__ == '__main__':
    main()

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

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