#include <bits/stdc++.h>

using namespace std;

using ll = long long;
using ul = unsigned long;
using ull = unsigned long long;

int main()
{
	ios::sync_with_stdio(false);
	cin.tie(nullptr);

	double a, b;
	cin >> a >> b;

	double res1, res2, res;
	res1 = 2 * M_PI * abs(a);
	res2 = 2 * M_PI * abs(b);

	if (a * b > 0)
		res = abs(res1 - res2);
	else
		res = res1 + res2;

	cout << fixed << setprecision(15) << res << "\n";

	return 0;
}