#include <bits/stdc++.h>
#define ull unsigned long long
#define ll long long
#define el endl
#define nl '\n'
#define all(v) v.begin(), v.end()
using namespace std;

void input()
{
    if (fopen("in.txt", "r"))
    {
        freopen("in.txt", "r", stdin);
        freopen("out.txt", "w", stdout);
    }
}

void init()
{
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
}
int main()
{
Fast:
    input();
    init();
    //---------------------------------------------------------------------------------------------------------------
    int r = 0;
    cin >> r;
    const double Pi = 3.14159;
    cout << Pi * pow(r, 2) << nl;

    return 0;
}