// LAB #1
#include <iostream>
#include <math.h>
using namespace std;

int main()
{
	double PI,R,square;
    PI = 3.14159;
	cout << "Input length:" << endl;
	cin >> R;
	square = 2*PI*pow(R,2);
	cout << "Square: " << square << endl;
	system("pause");
    return 0;
}