#include<bits/stdc++.h> // cin\cout\endl #include<cstdio> //scanf()\printf() #include<cstring> // strcpy()\strcat()\strcmp()\strlen()\memset() #include<cmath> //sqrt()\pow()\abs()\ceil()\floor()\max()\min() using namespace std; int main(){ double r; const double pi=3.1415926; cin>>r; double s=pi*r*r; cout<<fixed<<setprecision(2)<<s<<endl; return 0; }