#include <bits/stdc++.h>

using namespace std;
const double pi = atan(1.0) * 4;

int main() {
    for (double r; cin >> r;) {
        cout << fixed << setprecision(3)
             << 4.0 * pi * pow(r, 3) / 3 << endl;
    }
    return 0;
}