## The area of a circle

DaLongggggg 2021-04-06 20:05:57
area circle

# Problem description

Radius of given circle r, Find the area of a circle .

# Input format

Input contains an integer r, Represents the radius of a circle .

# Output format

Output one line , Contains a real number , Round to decimal 7 position , Represents the area of a circle .

explain ： In the subject , Input is an integer , But the output is a real number .

On the problem of real number output , Please be sure to see the requirements of real output , For example, it is required to keep the decimal point after this question 7 position , Your program must be strict with the output 7 Decimal place , It's not good to output too many or too few decimal places , Would be considered wrong .

If there is no special explanation for the problem of real number output , Rounding is done by rounding .

4

50.2654825

1 <= r <= 10000.

# Tips

This problem requires high precision , Please note that π The value of should take a more accurate value . You can use constants to represent π, such as PI=3.14159265358979323, You can also use mathematical formulas to find π, such as PI=atan(1.0)*4.

``import mathr=int(input())if (r<=10000 and r>=1): s=math.pi*r*r print('%.7f'%s) #print("{:.7f}".format(s))``

Import math Library usage pi
Format seven decimal output

https://pythonmana.com/2021/04/20210406195818639e.html