#include <stdio.h>
int main(){
    // int 整数型，String 字符串型，float n 小数型,double 双精度型
    double r;
    double PI=3.14159;
    scanf("%lf",&r);
    printf("%.4f",r*r*PI);
    return 0;
}

#include <iostream>
using namespace std;
const double PI = 3.14159;
double r;
int main()
{
    cin >> r;
    printf("%.4lf\n", r * r * PI);
}

#include "bits/stdc++.h"
using namespace std;
#define int double
#define pai 3.14159
signed main(){
    int r;
    cin>>r;
    printf("%.4f",pai*r*r);
    return 0;
}

#include <stdio.h>
int main()
{
    double r,s;
    scanf("%lf",&r);
    s=3.14159*r*r;
    printf("%.4lf",s);
    return 0;
}//B站搜索关注Siglota喵

#include<iostream>
using namespace std;
#include<iomanip>
	int main(){
	const	double p1=3.14159;
	double r;
	cin>>r;
	cout<<fixed<<setprecision(4)<<p1*r*r<<endl;
return 0;
}

import java.util.*;
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        double r = in.nextDouble();
        double pi = 3.14159;
        double s = r * r * pi;
        System.out.printf("%.4f", s);
    }
}

#include <stdio.h> 
int main()
{
	double a,c;
	scanf("%lf",&a);
	c=a*a*3.14159;
	printf("%.4lf",c);
	
	
	return 0;
 } 

#include<stdio.h>

#define pi 3.14159

int main(){

double r;

scanf("%lf",&r);

printf("%.4lf",rrpi);

return 0;

}

#include<iostream>
using namespace std;
#include <cstdio>
int main() {
    double r;
    const double PI = 3.14159;
    cin >> r;
    double val = PI * r * r;
    printf("%.4f", val);
}