#include <iostream>
#include <cmath>
#include <math.h>
#define M_PI           3.14159265358979323846
using namespace std;

int main() {
	// your code goes here
	int a,d,b;
	float p;
	cout << "Vnesi vrednost za plostinata na krug:\n";
	cin >>a;
	p = sqrt(a/M_PI);
            cout<<"Perimetar na pravoagolnikt e:"<<2*p*M_PI;

	return 0;
}