C :

#include <stdio.h>
int main(){
	int n;
	scanf("%d",&n);
	
	printf("%.2f\n%.2f",3.1415926 * n * n,3.1415926*2*n);


	return 0;
}

C++ :

#include <iostream>
#include <iomanip>

using namespace std;

int main(){
	int r;
	cin>>r;
	double pi = 3.1415926,s,c;
	s = pi * r * r;
	c = pi * 2 * r;
	cout<<fixed<<setprecision(2)<<s<<endl;
	cout<<fixed<<setprecision(2)<<c<<endl;
	return 0;
}

Python :

r = int(input())
s = 3.1415926 * r * r;
c = 3.1415926 * r * 2;
print('%.2f' % s)
print('%.2f' % c)