#include <bits/stdc++>
typedef long long ll;
#define rep(i,n) for(int i=0, i##_end=(n); i<i##_end; i++)
void debug_out() { cout << endl; }
template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
  cout << H << " ";
  debug_out(T...);
}
template<class T>bool updatemMax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>bool updateMin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }
#ifdef _DEBUG
#define debug(...) debug_out(__VA_ARGS__)
#else
#define debug(...) 
#endif
using std::cout ;
using std::endl ;
using std::cin ;
using std::string ;
using std::vector ;
using std::pair ;

int main()
{
    double R;
    cin >> R;
    
    double pi = 3.14159;
    
    cout << (pi*R*R) << endl;
}
