#include<iostream> #include<cstdio> #include<cstring> #include<cmath> #include<bits/stdc++.h> using namespace std; int main(){ /*int a; cin>>a; b=a%10; a=a/10; a=a+b*1000; cout<<a<<endl;*/ double n,c; cin>>n; c=n*3.1415926*n; printf("%.2lf",c); return 0; }